comparison modules/system/system.api.php @ 0:ff03f76ab3fe

initial version

+<?php
+
+/**
+ * @file
+ * Hooks provided by Drupal core and the System module.
+ */
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Defines one or more hooks that are exposed by a module.
+ *
+ * Normally hooks do not need to be explicitly defined. However, by declaring a
+ * hook explicitly, a module may define a "group" for it. Modules that implement
+ * a hook may then place their implementation in either $module.module or in
+ * $module.$group.inc. If the hook is located in $module.$group.inc, then that
+ * file will be automatically loaded when needed.
+ * In general, hooks that are rarely invoked and/or are very large should be
+ * placed in a separate include file, while hooks that are very short or very
+ * frequently called should be left in the main module file so that they are
+ * always available.
+ *
+ * @return
+ *   An associative array whose keys are hook names and whose values are an
+ *   associative array containing:
+ *   - group: A string defining the group to which the hook belongs. The module
+ *     system will determine whether a file with the name $module.$group.inc
+ *     exists, and automatically load it when required.
+ *
+ * See system_hook_info() for all hook groups defined by Drupal core.
+ *
+ * @see hook_hook_info_alter().
+ */
+function hook_hook_info() {
+  $hooks['token_info'] = array(
+    'group' => 'tokens',
+  );
+  $hooks['tokens'] = array(
+    'group' => 'tokens',
+  );
+  return $hooks;
+}
+
+/**
+ * Alter information from hook_hook_info().
+ *
+ * @param $hooks
+ *   Information gathered by module_hook_info() from other modules'
+ *   implementations of hook_hook_info(). Alter this array directly.
+ *   See hook_hook_info() for information on what this may contain.
+ */
+function hook_hook_info_alter(&$hooks) {
+  // Our module wants to completely override the core tokens, so make
+  // sure the core token hooks are not found.
+  $hooks['token_info']['group'] = 'mytokens';
+  $hooks['tokens']['group'] = 'mytokens';
+}
+
+/**
+ * Inform the base system and the Field API about one or more entity types.
+ *
+ * Inform the system about one or more entity types (i.e., object types that
+ * can be loaded via entity_load() and, optionally, to which fields can be
+ * attached).
+ *
+ * @return
+ *   An array whose keys are entity type names and whose values identify
+ *   properties of those types that the system needs to know about:
+ *   - label: The human-readable name of the type.
+ *   - controller class: The name of the class that is used to load the objects.
+ *     The class has to implement the DrupalEntityControllerInterface interface.
+ *     Leave blank to use the DrupalDefaultEntityController implementation.
+ *   - base table: (used by DrupalDefaultEntityController) The name of the
+ *     entity type's base table.
+ *   - revision table: The name of the entity type's revision table (if any).
+ *   - static cache: (used by DrupalDefaultEntityController) FALSE to disable
+ *     static caching of entities during a page request. Defaults to TRUE.
+ *   - field cache: (used by Field API loading and saving of field data) FALSE
+ *     to disable Field API's persistent cache of field data. Only recommended
+ *     if a higher level persistent cache is available for the entity type.
+ *     Defaults to TRUE.
+ *   - load hook: The name of the hook which should be invoked by
+ *     DrupalDefaultEntityController:attachLoad(), for example 'node_load'.
+ *   - uri callback: The name of an implementation of
+ *     callback_entity_info_uri().
+ *   - label callback: (optional) The name of an implementation of
+ *     callback_entity_info_label(), which returns the label of the entity. The
+ *     entity label is the main string associated with an entity; for example,
+ *     the title of a node or the subject of a comment. If there is an entity
+ *     object property that defines the label, then using the 'label' element of
+ *     the 'entity keys' return value component suffices to provide this
+ *     information (see below). Alternatively, specifying this callback allows
+ *     more complex logic to determine the label of an entity. See also the
+ *     entity_label() function, which implements this logic.
+ *   - language callback: (optional) The name of an implementation of
+ *     callback_entity_info_language(). In most situations, when needing to
+ *     determine this value, inspecting a property named after the 'language'
+ *     element of the 'entity keys' should be enough. The language callback is
+ *     meant to be used primarily for temporary alterations of the property
+ *     value: entity-defining modules are encouraged to always define a
+ *     language property, instead of using the callback as main entity language
+ *     source. In fact not having a language property defined is likely to
+ *     prevent an entity from being queried by language. Moreover, given that
+ *     entity_language() is not necessarily used everywhere it would be
+ *     appropriate, modules implementing the language callback should be aware
+ *     that this might not be always called.
+ *   - fieldable: Set to TRUE if you want your entity type to accept fields
+ *     being attached to it.
+ *   - translation: An associative array of modules registered as field
+ *     translation handlers. Array keys are the module names, array values
+ *     can be any data structure the module uses to provide field translation.
+ *     Any empty value disallows the module to appear as a translation handler.
+ *   - entity keys: An array describing how the Field API can extract the
+ *     information it needs from the objects of the type. Elements:
+ *     - id: The name of the property that contains the primary id of the
+ *       entity. Every entity object passed to the Field API must have this
+ *       property and its value must be numeric.
+ *     - revision: The name of the property that contains the revision id of
+ *       the entity. The Field API assumes that all revision ids are unique
+ *       across all entities of a type. This entry can be omitted if the
+ *       entities of this type are not versionable.
+ *     - bundle: The name of the property that contains the bundle name for the
+ *       entity. The bundle name defines which set of fields are attached to
+ *       the entity (e.g. what nodes call "content type"). This entry can be
+ *       omitted if this entity type exposes a single bundle (all entities have
+ *       the same collection of fields). The name of this single bundle will be
+ *       the same as the entity type.
+ *     - label: The name of the property that contains the entity label. For
+ *       example, if the entity's label is located in $entity->subject, then
+ *       'subject' should be specified here. If complex logic is required to
+ *       build the label, a 'label callback' should be defined instead (see
+ *       the 'label callback' section above for details).
+ *     - language: The name of the property, typically 'language', that contains
+ *       the language code representing the language the entity has been created
+ *       in. This value may be changed when editing the entity and represents
+ *       the language its textual components are supposed to have. If no
+ *       language property is available, the 'language callback' may be used
+ *       instead. This entry can be omitted if the entities of this type are not
+ *       language-aware.
+ *   - bundle keys: An array describing how the Field API can extract the
+ *     information it needs from the bundle objects for this type. This entry
+ *     is required if the 'path' provided in the 'bundles'/'admin' section
+ *     identifies the bundle using a named menu placeholder whose loader
+ *     callback returns an object (e.g., $vocabulary for taxonomy terms, or
+ *     $node_type for nodes). If the path does not include the bundle, or the
+ *     bundle is just a string rather than an automatically loaded object, then
+ *     this can be omitted. Elements:
+ *     - bundle: The name of the property of the bundle object that contains
+ *       the name of the bundle object.
+ *   - bundles: An array describing all bundles for this object type. Keys are
+ *     bundles machine names, as found in the objects' 'bundle' property
+ *     (defined in the 'entity keys' entry above). This entry can be omitted if
+ *     this entity type exposes a single bundle (all entities have the same
+ *     collection of fields). The name of this single bundle will be the same as
+ *     the entity type. Elements:
+ *     - label: The human-readable name of the bundle.
+ *     - uri callback: Same as the 'uri callback' key documented above for the
+ *       entity type, but for the bundle only. When determining the URI of an
+ *       entity, if a 'uri callback' is defined for both the entity type and
+ *       the bundle, the one for the bundle is used.
+ *     - admin: An array of information that allows Field UI pages to attach
+ *       themselves to the existing administration pages for the bundle.
+ *       Elements:
+ *       - path: the path of the bundle's main administration page, as defined
+ *         in hook_menu(). If the path includes a placeholder for the bundle,
+ *         the 'bundle argument' and 'real path' keys below are required.
+ *       - bundle argument: The position of the bundle placeholder in 'path', if
+ *         any.
+ *       - real path: The actual path (no placeholder) of the bundle's main
+ *         administration page. This will be used to generate links.
+ *       - access callback: As in hook_menu(). 'user_access' will be assumed if
+ *         no value is provided.
+ *       - access arguments: As in hook_menu().
+ *   - view modes: An array describing the view modes for the entity type. View
+ *     modes let entities be displayed differently depending on the context.
+ *     For instance, a node can be displayed differently on its own page
+ *     ('full' mode), on the home page or taxonomy listings ('teaser' mode), or
+ *     in an RSS feed ('rss' mode). Modules taking part in the display of the
+ *     entity (notably the Field API) can adjust their behavior depending on
+ *     the requested view mode. An additional 'default' view mode is available
+ *     for all entity types. This view mode is not intended for actual entity
+ *     display, but holds default display settings. For each available view
+ *     mode, administrators can configure whether it should use its own set of
+ *     field display settings, or just replicate the settings of the 'default'
+ *     view mode, thus reducing the amount of display configurations to keep
+ *     track of. Keys of the array are view mode names. Each view mode is
+ *     described by an array with the following key/value pairs:
+ *     - label: The human-readable name of the view mode
+ *     - custom settings: A boolean specifying whether the view mode should by
+ *       default use its own custom field display settings. If FALSE, entities
+ *       displayed in this view mode will reuse the 'default' display settings
+ *       by default (e.g. right after the module exposing the view mode is
+ *       enabled), but administrators can later use the Field UI to apply custom
+ *       display settings specific to the view mode.
+ *
+ * @see entity_load()
+ * @see hook_entity_info_alter()
+ */
+function hook_entity_info() {
+  $return = array(
+    'node' => array(
+      'label' => t('Node'),
+      'controller class' => 'NodeController',
+      'base table' => 'node',
+      'revision table' => 'node_revision',
+      'uri callback' => 'node_uri',
+      'fieldable' => TRUE,
+      'translation' => array(
+        'locale' => TRUE,
+      ),
+      'entity keys' => array(
+        'id' => 'nid',
+        'revision' => 'vid',
+        'bundle' => 'type',
+        'language' => 'language',
+      ),
+      'bundle keys' => array(
+        'bundle' => 'type',
+      ),
+      'bundles' => array(),
+      'view modes' => array(
+        'full' => array(
+          'label' => t('Full content'),
+          'custom settings' => FALSE,
+        ),
+        'teaser' => array(
+          'label' => t('Teaser'),
+          'custom settings' => TRUE,
+        ),
+        'rss' => array(
+          'label' => t('RSS'),
+          'custom settings' => FALSE,
+        ),
+      ),
+    ),
+  );
+
+  // Search integration is provided by node.module, so search-related
+  // view modes for nodes are defined here and not in search.module.
+  if (module_exists('search')) {
+    $return['node']['view modes'] += array(
+      'search_index' => array(
+        'label' => t('Search index'),
+        'custom settings' => FALSE,
+      ),
+      'search_result' => array(
+        'label' => t('Search result'),
+        'custom settings' => FALSE,
+      ),
+    );
+  }
+
+  // Bundles must provide a human readable name so we can create help and error
+  // messages, and the path to attach Field admin pages to.
+  foreach (node_type_get_names() as $type => $name) {
+    $return['node']['bundles'][$type] = array(
+      'label' => $name,
+      'admin' => array(
+        'path' => 'admin/structure/types/manage/%node_type',
+        'real path' => 'admin/structure/types/manage/' . str_replace('_', '-', $type),
+        'bundle argument' => 4,
+        'access arguments' => array('administer content types'),
+      ),
+    );
+  }
+
+  return $return;
+}
+
+/**
+ * Alter the entity info.
+ *
+ * Modules may implement this hook to alter the information that defines an
+ * entity. All properties that are available in hook_entity_info() can be
+ * altered here.
+ *
+ * @param $entity_info
+ *   The entity info array, keyed by entity name.
+ *
+ * @see hook_entity_info()
+ */
+function hook_entity_info_alter(&$entity_info) {
+  // Set the controller class for nodes to an alternate implementation of the
+  // DrupalEntityController interface.
+  $entity_info['node']['controller class'] = 'MyCustomNodeController';
+}
+
+/**
+ * Act on entities when loaded.
+ *
+ * This is a generic load hook called for all entity types loaded via the
+ * entity API.
+ *
+ * @param $entities
+ *   The entities keyed by entity ID.
+ * @param $type
+ *   The type of entities being loaded (i.e. node, user, comment).
+ */
+function hook_entity_load($entities, $type) {
+  foreach ($entities as $entity) {
+    $entity->foo = mymodule_add_something($entity, $type);
+  }
+}
+
+/**
+ * Act on an entity before it is about to be created or updated.
+ *
+ * @param $entity
+ *   The entity object.
+ * @param $type
+ *   The type of entity being saved (i.e. node, user, comment).
+ */
+function hook_entity_presave($entity, $type) {
+  $entity->changed = REQUEST_TIME;
+}
+
+/**
+ * Act on entities when inserted.
+ *
+ * @param $entity
+ *   The entity object.
+ * @param $type
+ *   The type of entity being inserted (i.e. node, user, comment).
+ */
+function hook_entity_insert($entity, $type) {
+  // Insert the new entity into a fictional table of all entities.
+  $info = entity_get_info($type);
+  list($id) = entity_extract_ids($type, $entity);
+  db_insert('example_entity')
+    ->fields(array(
+      'type' => $type,
+      'id' => $id,
+      'created' => REQUEST_TIME,
+      'updated' => REQUEST_TIME,
+    ))
+    ->execute();
+}
+
+/**
+ * Act on entities when updated.
+ *
+ * @param $entity
+ *   The entity object.
+ * @param $type
+ *   The type of entity being updated (i.e. node, user, comment).
+ */
+function hook_entity_update($entity, $type) {
+  // Update the entity's entry in a fictional table of all entities.
+  $info = entity_get_info($type);
+  list($id) = entity_extract_ids($type, $entity);
+  db_update('example_entity')
+    ->fields(array(
+      'updated' => REQUEST_TIME,
+    ))
+    ->condition('type', $type)
+    ->condition('id', $id)
+    ->execute();
+}
+
+/**
+ * Act on entities when deleted.
+ *
+ * @param $entity
+ *   The entity object.
+ * @param $type
+ *   The type of entity being deleted (i.e. node, user, comment).
+ */
+function hook_entity_delete($entity, $type) {
+  // Delete the entity's entry from a fictional table of all entities.
+  $info = entity_get_info($type);
+  list($id) = entity_extract_ids($type, $entity);
+  db_delete('example_entity')
+    ->condition('type', $type)
+    ->condition('id', $id)
+    ->execute();
+}
+
+/**
+ * Alter or execute an EntityFieldQuery.
+ *
+ * @param EntityFieldQuery $query
+ *   An EntityFieldQuery. One of the most important properties to be changed is
+ *   EntityFieldQuery::executeCallback. If this is set to an existing function,
+ *   this function will get the query as its single argument and its result
+ *   will be the returned as the result of EntityFieldQuery::execute(). This can
+ *   be used to change the behavior of EntityFieldQuery entirely. For example,
+ *   the default implementation can only deal with one field storage engine, but
+ *   it is possible to write a module that can query across field storage
+ *   engines. Also, the default implementation presumes entities are stored in
+ *   SQL, but the execute callback could instead query any other entity storage,
+ *   local or remote.
+ *
+ *   Note the $query->altered attribute which is TRUE in case the query has
+ *   already been altered once. This happens with cloned queries.
+ *   If there is a pager, then such a cloned query will be executed to count
+ *   all elements. This query can be detected by checking for
+ *   ($query->pager && $query->count), allowing the driver to return 0 from
+ *   the count query and disable the pager.
+ */
+function hook_entity_query_alter($query) {
+  $query->executeCallback = 'my_module_query_callback';
+}
+
+/**
+ * Act on entities being assembled before rendering.
+ *
+ * @param $entity
+ *   The entity object.
+ * @param $type
+ *   The type of entity being rendered (i.e. node, user, comment).
+ * @param $view_mode
+ *   The view mode the entity is rendered in.
+ * @param $langcode
+ *   The language code used for rendering.
+ *
+ * The module may add elements to $entity->content prior to rendering. The
+ * structure of $entity->content is a renderable array as expected by
+ * drupal_render().
+ *
+ * @see hook_entity_view_alter()
+ * @see hook_comment_view()
+ * @see hook_node_view()
+ * @see hook_user_view()
+ */
+function hook_entity_view($entity, $type, $view_mode, $langcode) {
+  $entity->content['my_additional_field'] = array(
+    '#markup' => $additional_field,
+    '#weight' => 10,
+    '#theme' => 'mymodule_my_additional_field',
+  );
+}
+
+/**
+ * Alter the results of ENTITY_view().
+ *
+ * This hook is called after the content has been assembled in a structured
+ * array and may be used for doing processing which requires that the complete
+ * entity content structure has been built.
+ *
+ * If a module wishes to act on the rendered HTML of the entity rather than the
+ * structured content array, it may use this hook to add a #post_render
+ * callback. Alternatively, it could also implement hook_preprocess_ENTITY().
+ * See drupal_render() and theme() for details.
+ *
+ * @param $build
+ *   A renderable array representing the entity content.
+ * @param $type
+ *   The type of entity being rendered (i.e. node, user, comment).
+ *
+ * @see hook_entity_view()
+ * @see hook_comment_view_alter()
+ * @see hook_node_view_alter()
+ * @see hook_taxonomy_term_view_alter()
+ * @see hook_user_view_alter()
+ */
+function hook_entity_view_alter(&$build, $type) {
+  if ($build['#view_mode'] == 'full' && isset($build['an_additional_field'])) {
+    // Change its weight.
+    $build['an_additional_field']['#weight'] = -10;
+
+    // Add a #post_render callback to act on the rendered HTML of the entity.
+    $build['#post_render'][] = 'my_module_node_post_render';
+  }
+}
+
+/**
+ * Change the view mode of an entity that is being displayed.
+ *
+ * @param string $view_mode
+ *   The view_mode that is to be used to display the entity.
+ * @param array $context
+ *   Array with contextual information, including:
+ *   - entity_type: The type of the entity that is being viewed.
+ *   - entity: The entity object.
+ *   - langcode: The langcode the entity is being viewed in.
+ */
+function hook_entity_view_mode_alter(&$view_mode, $context) {
+  // For nodes, change the view mode when it is teaser.
+  if ($context['entity_type'] == 'node' && $view_mode == 'teaser') {
+    $view_mode = 'my_custom_view_mode';
+  }
+}
+
+/**
+ * Define administrative paths.
+ *
+ * Modules may specify whether or not the paths they define in hook_menu() are
+ * to be considered administrative. Other modules may use this information to
+ * display those pages differently (e.g. in a modal overlay, or in a different
+ * theme).
+ *
+ * To change the administrative status of menu items defined in another module's
+ * hook_menu(), modules should implement hook_admin_paths_alter().
+ *
+ * @return
+ *   An associative array. For each item, the key is the path in question, in
+ *   a format acceptable to drupal_match_path(). The value for each item should
+ *   be TRUE (for paths considered administrative) or FALSE (for non-
+ *   administrative paths).
+ *
+ * @see hook_menu()
+ * @see drupal_match_path()
+ * @see hook_admin_paths_alter()
+ */
+function hook_admin_paths() {
+  $paths = array(
+    'mymodule/*/add' => TRUE,
+    'mymodule/*/edit' => TRUE,
+  );
+  return $paths;
+}
+
+/**
+ * Redefine administrative paths defined by other modules.
+ *
+ * @param $paths
+ *   An associative array of administrative paths, as defined by implementations
+ *   of hook_admin_paths().
+ *
+ * @see hook_admin_paths()
+ */
+function hook_admin_paths_alter(&$paths) {
+  // Treat all user pages as administrative.
+  $paths['user'] = TRUE;
+  $paths['user/*'] = TRUE;
+  // Treat the forum topic node form as a non-administrative page.
+  $paths['node/add/forum'] = FALSE;
+}
+
+/**
+ * Act on entities as they are being prepared for view.
+ *
+ * Allows you to operate on multiple entities as they are being prepared for
+ * view. Only use this if attaching the data during the entity_load() phase
+ * is not appropriate, for example when attaching other 'entity' style objects.
+ *
+ * @param $entities
+ *   The entities keyed by entity ID.
+ * @param $type
+ *   The type of entities being loaded (i.e. node, user, comment).
+ * @param $langcode
+ *   The language to display the entity in.
+ */
+function hook_entity_prepare_view($entities, $type, $langcode) {
+  // Load a specific node into the user object for later theming.
+  if ($type == 'user') {
+    $nodes = mymodule_get_user_nodes(array_keys($entities));
+    foreach ($entities as $uid => $entity) {
+      $entity->user_node = $nodes[$uid];
+    }
+  }
+}
+
+/**
+ * Perform periodic actions.
+ *
+ * Modules that require some commands to be executed periodically can
+ * implement hook_cron(). The engine will then call the hook whenever a cron
+ * run happens, as defined by the administrator. Typical tasks managed by
+ * hook_cron() are database maintenance, backups, recalculation of settings
+ * or parameters, automated mailing, and retrieving remote data.
+ *
+ * Short-running or non-resource-intensive tasks can be executed directly in
+ * the hook_cron() implementation.
+ *
+ * Long-running tasks and tasks that could time out, such as retrieving remote
+ * data, sending email, and intensive file tasks, should use the queue API
+ * instead of executing the tasks directly. To do this, first define one or
+ * more queues via hook_cron_queue_info(). Then, add items that need to be
+ * processed to the defined queues.
+ */
+function hook_cron() {
+  // Short-running operation example, not using a queue:
+  // Delete all expired records since the last cron run.
+  $expires = variable_get('mymodule_cron_last_run', REQUEST_TIME);
+  db_delete('mymodule_table')
+    ->condition('expires', $expires, '>=')
+    ->execute();
+  variable_set('mymodule_cron_last_run', REQUEST_TIME);
+
+  // Long-running operation example, leveraging a queue:
+  // Fetch feeds from other sites.
+  $result = db_query('SELECT * FROM {aggregator_feed} WHERE checked + refresh < :time AND refresh <> :never', array(
+    ':time' => REQUEST_TIME,
+    ':never' => AGGREGATOR_CLEAR_NEVER,
+  ));
+  $queue = DrupalQueue::get('aggregator_feeds');
+  foreach ($result as $feed) {
+    $queue->createItem($feed);
+  }
+}
+
+/**
+ * Declare queues holding items that need to be run periodically.
+ *
+ * While there can be only one hook_cron() process running at the same time,
+ * there can be any number of processes defined here running. Because of
+ * this, long running tasks are much better suited for this API. Items queued
+ * in hook_cron() might be processed in the same cron run if there are not many
+ * items in the queue, otherwise it might take several requests, which can be
+ * run in parallel.
+ *
+ * @return
+ *   An associative array where the key is the queue name and the value is
+ *   again an associative array. Possible keys are:
+ *   - 'worker callback': The name of the function to call. It will be called
+ *     with one argument, the item created via DrupalQueue::createItem() in
+ *     hook_cron().
+ *   - 'time': (optional) How much time Drupal should spend on calling this
+ *     worker in seconds. Defaults to 15.
+ *
+ * @see hook_cron()
+ * @see hook_cron_queue_info_alter()
+ */
+function hook_cron_queue_info() {
+  $queues['aggregator_feeds'] = array(
+    'worker callback' => 'aggregator_refresh',
+    'time' => 60,
+  );
+  return $queues;
+}
+
+/**
+ * Alter cron queue information before cron runs.
+ *
+ * Called by drupal_cron_run() to allow modules to alter cron queue settings
+ * before any jobs are processesed.
+ *
+ * @param array $queues
+ *   An array of cron queue information.
+ *
+ * @see hook_cron_queue_info()
+ * @see drupal_cron_run()
+ */
+function hook_cron_queue_info_alter(&$queues) {
+  // This site has many feeds so let's spend 90 seconds on each cron run
+  // updating feeds instead of the default 60.
+  $queues['aggregator_feeds']['time'] = 90;
+}
+
+/**
+ * Allows modules to declare their own Form API element types and specify their
+ * default values.
+ *
+ * This hook allows modules to declare their own form element types and to
+ * specify their default values. The values returned by this hook will be
+ * merged with the elements returned by hook_form() implementations and so
+ * can return defaults for any Form APIs keys in addition to those explicitly
+ * mentioned below.
+ *
+ * Each of the form element types defined by this hook is assumed to have
+ * a matching theme function, e.g. theme_elementtype(), which should be
+ * registered with hook_theme() as normal.
+ *
+ * For more information about custom element types see the explanation at
+ * http://drupal.org/node/169815.
+ *
+ * @return
+ *  An associative array describing the element types being defined. The array
+ *  contains a sub-array for each element type, with the machine-readable type
+ *  name as the key. Each sub-array has a number of possible attributes:
+ *  - "#input": boolean indicating whether or not this element carries a value
+ *    (even if it's hidden).
+ *  - "#process": array of callback functions taking $element, $form_state,
+ *    and $complete_form.
+ *  - "#after_build": array of callback functions taking $element and $form_state.
+ *  - "#validate": array of callback functions taking $form and $form_state.
+ *  - "#element_validate": array of callback functions taking $element and
+ *    $form_state.
+ *  - "#pre_render": array of callback functions taking $element and $form_state.
+ *  - "#post_render": array of callback functions taking $element and $form_state.
+ *  - "#submit": array of callback functions taking $form and $form_state.
+ *  - "#title_display": optional string indicating if and how #title should be
+ *    displayed, see theme_form_element() and theme_form_element_label().
+ *
+ * @see hook_element_info_alter()
+ * @see system_element_info()
+ */
+function hook_element_info() {
+  $types['filter_format'] = array(
+    '#input' => TRUE,
+  );
+  return $types;
+}
+
+/**
+ * Alter the element type information returned from modules.
+ *
+ * A module may implement this hook in order to alter the element type defaults
+ * defined by a module.
+ *
+ * @param $type
+ *   All element type defaults as collected by hook_element_info().
+ *
+ * @see hook_element_info()
+ */
+function hook_element_info_alter(&$type) {
+  // Decrease the default size of textfields.
+  if (isset($type['textfield']['#size'])) {
+    $type['textfield']['#size'] = 40;
+  }
+}
+
+/**
+ * Perform cleanup tasks.
+ *
+ * This hook is run at the end of most regular page requests. It is often
+ * used for page logging and specialized cleanup. This hook MUST NOT print
+ * anything because by the time it runs the response is already sent to
+ * the browser.
+ *
+ * Only use this hook if your code must run even for cached page views.
+ * If you have code which must run once on all non-cached pages, use
+ * hook_init() instead. That is the usual case. If you implement this hook
+ * and see an error like 'Call to undefined function', it is likely that
+ * you are depending on the presence of a module which has not been loaded yet.
+ * It is not loaded because Drupal is still in bootstrap mode.
+ *
+ * @param $destination
+ *   If this hook is invoked as part of a drupal_goto() call, then this argument
+ *   will be a fully-qualified URL that is the destination of the redirect.
+ */
+function hook_exit($destination = NULL) {
+  db_update('counter')
+    ->expression('hits', 'hits + 1')
+    ->condition('type', 1)
+    ->execute();
+}
+
+/**
+ * Perform necessary alterations to the JavaScript before it is presented on
+ * the page.
+ *
+ * @param $javascript
+ *   An array of all JavaScript being presented on the page.
+ *
+ * @see drupal_add_js()
+ * @see drupal_get_js()
+ * @see drupal_js_defaults()
+ */
+function hook_js_alter(&$javascript) {
+  // Swap out jQuery to use an updated version of the library.
+  $javascript['misc/jquery.js']['data'] = drupal_get_path('module', 'jquery_update') . '/jquery.js';
+}
+
+/**
+ * Registers JavaScript/CSS libraries associated with a module.
+ *
+ * Modules implementing this return an array of arrays. The key to each
+ * sub-array is the machine readable name of the library. Each library may
+ * contain the following items:
+ *
+ * - 'title': The human readable name of the library.
+ * - 'website': The URL of the library's web site.
+ * - 'version': A string specifying the version of the library; intentionally
+ *   not a float because a version like "1.2.3" is not a valid float. Use PHP's
+ *   version_compare() to compare different versions.
+ * - 'js': An array of JavaScript elements; each element's key is used as $data
+ *   argument, each element's value is used as $options array for
+ *   drupal_add_js(). To add library-specific (not module-specific) JavaScript
+ *   settings, the key may be skipped, the value must specify
+ *   'type' => 'setting', and the actual settings must be contained in a 'data'
+ *   element of the value.
+ * - 'css': Like 'js', an array of CSS elements passed to drupal_add_css().
+ * - 'dependencies': An array of libraries that are required for a library. Each
+ *   element is an array listing the module and name of another library. Note
+ *   that all dependencies for each dependent library will also be added when
+ *   this library is added.
+ *
+ * Registered information for a library should contain re-usable data only.
+ * Module- or implementation-specific data and integration logic should be added
+ * separately.
+ *
+ * @return
+ *   An array defining libraries associated with a module.
+ *
+ * @see system_library()
+ * @see drupal_add_library()
+ * @see drupal_get_library()
+ */
+function hook_library() {
+  // Library One.
+  $libraries['library-1'] = array(
+    'title' => 'Library One',
+    'website' => 'http://example.com/library-1',
+    'version' => '1.2',
+    'js' => array(
+      drupal_get_path('module', 'my_module') . '/library-1.js' => array(),
+    ),
+    'css' => array(
+      drupal_get_path('module', 'my_module') . '/library-2.css' => array(
+        'type' => 'file',
+        'media' => 'screen',
+      ),
+    ),
+  );
+  // Library Two.
+  $libraries['library-2'] = array(
+    'title' => 'Library Two',
+    'website' => 'http://example.com/library-2',
+    'version' => '3.1-beta1',
+    'js' => array(
+      // JavaScript settings may use the 'data' key.
+      array(
+        'type' => 'setting',
+        'data' => array('library2' => TRUE),
+      ),
+    ),
+    'dependencies' => array(
+      // Require jQuery UI core by System module.
+      array('system', 'ui'),
+      // Require our other library.
+      array('my_module', 'library-1'),
+      // Require another library.
+      array('other_module', 'library-3'),
+    ),
+  );
+  return $libraries;
+}
+
+/**
+ * Alters the JavaScript/CSS library registry.
+ *
+ * Allows certain, contributed modules to update libraries to newer versions
+ * while ensuring backwards compatibility. In general, such manipulations should
+ * only be done by designated modules, since most modules that integrate with a
+ * certain library also depend on the API of a certain library version.
+ *
+ * @param $libraries
+ *   The JavaScript/CSS libraries provided by $module. Keyed by internal library
+ *   name and passed by reference.
+ * @param $module
+ *   The name of the module that registered the libraries.
+ *
+ * @see hook_library()
+ */
+function hook_library_alter(&$libraries, $module) {
+  // Update Farbtastic to version 2.0.
+  if ($module == 'system' && isset($libraries['farbtastic'])) {
+    // Verify existing version is older than the one we are updating to.
+    if (version_compare($libraries['farbtastic']['version'], '2.0', '<')) {
+      // Update the existing Farbtastic to version 2.0.
+      $libraries['farbtastic']['version'] = '2.0';
+      $libraries['farbtastic']['js'] = array(
+        drupal_get_path('module', 'farbtastic_update') . '/farbtastic-2.0.js' => array(),
+      );
+    }
+  }
+}
+
+/**
+ * Alter CSS files before they are output on the page.
+ *
+ * @param $css
+ *   An array of all CSS items (files and inline CSS) being requested on the page.
+ *
+ * @see drupal_add_css()
+ * @see drupal_get_css()
+ */
+function hook_css_alter(&$css) {
+  // Remove defaults.css file.
+  unset($css[drupal_get_path('module', 'system') . '/defaults.css']);
+}
+
+/**
+ * Alter the commands that are sent to the user through the Ajax framework.
+ *
+ * @param $commands
+ *   An array of all commands that will be sent to the user.
+ *
+ * @see ajax_render()
+ */
+function hook_ajax_render_alter($commands) {
+  // Inject any new status messages into the content area.
+  $commands[] = ajax_command_prepend('#block-system-main .content', theme('status_messages'));
+}
+
+/**
+ * Add elements to a page before it is rendered.
+ *
+ * Use this hook when you want to add elements at the page level. For your
+ * additions to be printed, they have to be placed below a top level array key
+ * of the $page array that has the name of a region of the active theme.
+ *
+ * By default, valid region keys are 'page_top', 'header', 'sidebar_first',
+ * 'content', 'sidebar_second' and 'page_bottom'. To get a list of all regions
+ * of the active theme, use system_region_list($theme). Note that $theme is a
+ * global variable.
+ *
+ * If you want to alter the elements added by other modules or if your module
+ * depends on the elements of other modules, use hook_page_alter() instead which
+ * runs after this hook.
+ *
+ * @param $page
+ *   Nested array of renderable elements that make up the page.
+ *
+ * @see hook_page_alter()
+ * @see drupal_render_page()
+ */
+function hook_page_build(&$page) {
+  if (menu_get_object('node', 1)) {
+    // We are on a node detail page. Append a standard disclaimer to the
+    // content region.
+    $page['content']['disclaimer'] = array(
+      '#markup' => t('Acme, Inc. is not responsible for the contents of this sample code.'),
+      '#weight' => 25,
+    );
+  }
+}
+
+/**
+ * Alter a menu router item right after it has been retrieved from the database or cache.
+ *
+ * This hook is invoked by menu_get_item() and allows for run-time alteration of router
+ * information (page_callback, title, and so on) before it is translated and checked for
+ * access. The passed-in $router_item is statically cached for the current request, so this
+ * hook is only invoked once for any router item that is retrieved via menu_get_item().
+ *
+ * Usually, modules will only want to inspect the router item and conditionally
+ * perform other actions (such as preparing a state for the current request).
+ * Note that this hook is invoked for any router item that is retrieved by
+ * menu_get_item(), which may or may not be called on the path itself, so implementations
+ * should check the $path parameter if the alteration should fire for the current request
+ * only.
+ *
+ * @param $router_item
+ *   The menu router item for $path.
+ * @param $path
+ *   The originally passed path, for which $router_item is responsible.
+ * @param $original_map
+ *   The path argument map, as contained in $path.
+ *
+ * @see menu_get_item()
+ */
+function hook_menu_get_item_alter(&$router_item, $path, $original_map) {
+  // When retrieving the router item for the current path...
+  if ($path == $_GET['q']) {
+    // ...call a function that prepares something for this request.
+    mymodule_prepare_something();
+  }
+}
+
+/**
+ * Define menu items and page callbacks.
+ *
+ * This hook enables modules to register paths in order to define how URL
+ * requests are handled. Paths may be registered for URL handling only, or they
+ * can register a link to be placed in a menu (usually the Navigation menu). A
+ * path and its associated information is commonly called a "menu router item".
+ * This hook is rarely called (for example, when modules are enabled), and
+ * its results are cached in the database.
+ *
+ * hook_menu() implementations return an associative array whose keys define
+ * paths and whose values are an associative array of properties for each
+ * path. (The complete list of properties is in the return value section below.)
+ *
+ * @section sec_callback_funcs Callback Functions
+ * The definition for each path may include a page callback function, which is
+ * invoked when the registered path is requested. If there is no other
+ * registered path that fits the requested path better, any further path
+ * components are passed to the callback function. For example, your module
+ * could register path 'abc/def':
+ * @code
+ *   function mymodule_menu() {
+ *     $items['abc/def'] = array(
+ *       'page callback' => 'mymodule_abc_view',
+ *     );
+ *     return $items;
+ *   }
+ *
+ *   function mymodule_abc_view($ghi = 0, $jkl = '') {
+ *     // ...
+ *   }
+ * @endcode
+ * When path 'abc/def' is requested, no further path components are in the
+ * request, and no additional arguments are passed to the callback function (so
+ * $ghi and $jkl would take the default values as defined in the function
+ * signature). When 'abc/def/123/foo' is requested, $ghi will be '123' and
+ * $jkl will be 'foo'. Note that this automatic passing of optional path
+ * arguments applies only to page and theme callback functions.
+ *
+ * @subsection sub_callback_arguments Callback Arguments
+ * In addition to optional path arguments, the page callback and other callback
+ * functions may specify argument lists as arrays. These argument lists may
+ * contain both fixed/hard-coded argument values and integers that correspond
+ * to path components. When integers are used and the callback function is
+ * called, the corresponding path components will be substituted for the
+ * integers. That is, the integer 0 in an argument list will be replaced with
+ * the first path component, integer 1 with the second, and so on (path
+ * components are numbered starting from zero). To pass an integer without it
+ * being replaced with its respective path component, use the string value of
+ * the integer (e.g., '1') as the argument value. This substitution feature
+ * allows you to re-use a callback function for several different paths. For
+ * example:
+ * @code
+ *   function mymodule_menu() {
+ *     $items['abc/def'] = array(
+ *       'page callback' => 'mymodule_abc_view',
+ *       'page arguments' => array(1, 'foo'),
+ *     );
+ *     return $items;
+ *   }
+ * @endcode
+ * When path 'abc/def' is requested, the page callback function will get 'def'
+ * as the first argument and (always) 'foo' as the second argument.
+ *
+ * If a page callback function uses an argument list array, and its path is
+ * requested with optional path arguments, then the list array's arguments are
+ * passed to the callback function first, followed by the optional path
+ * arguments. Using the above example, when path 'abc/def/bar/baz' is requested,
+ * mymodule_abc_view() will be called with 'def', 'foo', 'bar' and 'baz' as
+ * arguments, in that order.
+ *
+ * Special care should be taken for the page callback drupal_get_form(), because
+ * your specific form callback function will always receive $form and
+ * &$form_state as the first function arguments:
+ * @code
+ *   function mymodule_abc_form($form, &$form_state) {
+ *     // ...
+ *     return $form;
+ *   }
+ * @endcode
+ * See @link form_api Form API documentation @endlink for details.
+ *
+ * @section sec_path_wildcards Wildcards in Paths
+ * @subsection sub_simple_wildcards Simple Wildcards
+ * Wildcards within paths also work with integer substitution. For example,
+ * your module could register path 'my-module/%/edit':
+ * @code
+ *   $items['my-module/%/edit'] = array(
+ *     'page callback' => 'mymodule_abc_edit',
+ *     'page arguments' => array(1),
+ *   );
+ * @endcode
+ * When path 'my-module/foo/edit' is requested, integer 1 will be replaced
+ * with 'foo' and passed to the callback function. Note that wildcards may not
+ * be used as the first component.
+ *
+ * @subsection sub_autoload_wildcards Auto-Loader Wildcards
+ * Registered paths may also contain special "auto-loader" wildcard components
+ * in the form of '%mymodule_abc', where the '%' part means that this path
+ * component is a wildcard, and the 'mymodule_abc' part defines the prefix for a
+ * load function, which here would be named mymodule_abc_load(). When a matching
+ * path is requested, your load function will receive as its first argument the
+ * path component in the position of the wildcard; load functions may also be
+ * passed additional arguments (see "load arguments" in the return value
+ * section below). For example, your module could register path
+ * 'my-module/%mymodule_abc/edit':
+ * @code
+ *   $items['my-module/%mymodule_abc/edit'] = array(
+ *     'page callback' => 'mymodule_abc_edit',
+ *     'page arguments' => array(1),
+ *   );
+ * @endcode
+ * When path 'my-module/123/edit' is requested, your load function
+ * mymodule_abc_load() will be invoked with the argument '123', and should
+ * load and return an "abc" object with internal id 123:
+ * @code
+ *   function mymodule_abc_load($abc_id) {
+ *     return db_query("SELECT * FROM {mymodule_abc} WHERE abc_id = :abc_id", array(':abc_id' => $abc_id))->fetchObject();
+ *   }
+ * @endcode
+ * This 'abc' object will then be passed into the callback functions defined
+ * for the menu item, such as the page callback function mymodule_abc_edit()
+ * to replace the integer 1 in the argument array. Note that a load function
+ * should return FALSE when it is unable to provide a loadable object. For
+ * example, the node_load() function for the 'node/%node/edit' menu item will
+ * return FALSE for the path 'node/999/edit' if a node with a node ID of 999
+ * does not exist. The menu routing system will return a 404 error in this case.
+ *
+ * @subsection sub_argument_wildcards Argument Wildcards
+ * You can also define a %wildcard_to_arg() function (for the example menu
+ * entry above this would be 'mymodule_abc_to_arg()'). The _to_arg() function
+ * is invoked to retrieve a value that is used in the path in place of the
+ * wildcard. A good example is user.module, which defines
+ * user_uid_optional_to_arg() (corresponding to the menu entry
+ * 'tracker/%user_uid_optional'). This function returns the user ID of the
+ * current user.
+ *
+ * The _to_arg() function will get called with three arguments:
+ * - $arg: A string representing whatever argument may have been supplied by
+ *   the caller (this is particularly useful if you want the _to_arg()
+ *   function only supply a (default) value if no other value is specified,
+ *   as in the case of user_uid_optional_to_arg().
+ * - $map: An array of all path fragments (e.g. array('node','123','edit') for
+ *   'node/123/edit').
+ * - $index: An integer indicating which element of $map corresponds to $arg.
+ *
+ * _load() and _to_arg() functions may seem similar at first glance, but they
+ * have different purposes and are called at different times. _load()
+ * functions are called when the menu system is collecting arguments to pass
+ * to the callback functions defined for the menu item. _to_arg() functions
+ * are called when the menu system is generating links to related paths, such
+ * as the tabs for a set of MENU_LOCAL_TASK items.
+ *
+ * @section sec_render_tabs Rendering Menu Items As Tabs
+ * You can also make groups of menu items to be rendered (by default) as tabs
+ * on a page. To do that, first create one menu item of type MENU_NORMAL_ITEM,
+ * with your chosen path, such as 'foo'. Then duplicate that menu item, using a
+ * subdirectory path, such as 'foo/tab1', and changing the type to
+ * MENU_DEFAULT_LOCAL_TASK to make it the default tab for the group. Then add
+ * the additional tab items, with paths such as "foo/tab2" etc., with type
+ * MENU_LOCAL_TASK. Example:
+ * @code
+ * // Make "Foo settings" appear on the admin Config page
+ * $items['admin/config/system/foo'] = array(
+ *   'title' => 'Foo settings',
+ *   'type' => MENU_NORMAL_ITEM,
+ *   // Page callback, etc. need to be added here.
+ * );
+ * // Make "Tab 1" the main tab on the "Foo settings" page
+ * $items['admin/config/system/foo/tab1'] = array(
+ *   'title' => 'Tab 1',
+ *   'type' => MENU_DEFAULT_LOCAL_TASK,
+ *   // Access callback, page callback, and theme callback will be inherited
+ *   // from 'admin/config/system/foo', if not specified here to override.
+ * );
+ * // Make an additional tab called "Tab 2" on "Foo settings"
+ * $items['admin/config/system/foo/tab2'] = array(
+ *   'title' => 'Tab 2',
+ *   'type' => MENU_LOCAL_TASK,
+ *   // Page callback and theme callback will be inherited from
+ *   // 'admin/config/system/foo', if not specified here to override.
+ *   // Need to add access callback or access arguments.
+ * );
+ * @endcode
+ *
+ * @return
+ *   An array of menu items. Each menu item has a key corresponding to the
+ *   Drupal path being registered. The corresponding array value is an
+ *   associative array that may contain the following key-value pairs:
+ *   - "title": Required. The untranslated title of the menu item.
+ *   - "title callback": Function to generate the title; defaults to t().
+ *     If you require only the raw string to be output, set this to FALSE.
+ *   - "title arguments": Arguments to send to t() or your custom callback,
+ *     with path component substitution as described above.
+ *   - "description": The untranslated description of the menu item.
+ *   - "page callback": The function to call to display a web page when the user
+ *     visits the path. If omitted, the parent menu item's callback will be used
+ *     instead.
+ *   - "page arguments": An array of arguments to pass to the page callback
+ *     function, with path component substitution as described above.
+ *   - "delivery callback": The function to call to package the result of the
+ *     page callback function and send it to the browser. Defaults to
+ *     drupal_deliver_html_page() unless a value is inherited from a parent menu
+ *     item. Note that this function is called even if the access checks fail,
+ *     so any custom delivery callback function should take that into account.
+ *     See drupal_deliver_html_page() for an example.
+ *   - "access callback": A function returning TRUE if the user has access
+ *     rights to this menu item, and FALSE if not. It can also be a boolean
+ *     constant instead of a function, and you can also use numeric values
+ *     (will be cast to boolean). Defaults to user_access() unless a value is
+ *     inherited from the parent menu item; only MENU_DEFAULT_LOCAL_TASK items
+ *     can inherit access callbacks. To use the user_access() default callback,
+ *     you must specify the permission to check as 'access arguments' (see
+ *     below).
+ *   - "access arguments": An array of arguments to pass to the access callback
+ *     function, with path component substitution as described above. If the
+ *     access callback is inherited (see above), the access arguments will be
+ *     inherited with it, unless overridden in the child menu item.
+ *   - "theme callback": (optional) A function returning the machine-readable
+ *     name of the theme that will be used to render the page. If not provided,
+ *     the value will be inherited from a parent menu item. If there is no
+ *     theme callback, or if the function does not return the name of a current
+ *     active theme on the site, the theme for this page will be determined by
+ *     either hook_custom_theme() or the default theme instead. As a general
+ *     rule, the use of theme callback functions should be limited to pages
+ *     whose functionality is very closely tied to a particular theme, since
+ *     they can only be overridden by modules which specifically target those
+ *     pages in hook_menu_alter(). Modules implementing more generic theme
+ *     switching functionality (for example, a module which allows the theme to
+ *     be set dynamically based on the current user's role) should use
+ *     hook_custom_theme() instead.
+ *   - "theme arguments": An array of arguments to pass to the theme callback
+ *     function, with path component substitution as described above.
+ *   - "file": A file that will be included before the page callback is called;
+ *     this allows page callback functions to be in separate files. The file
+ *     should be relative to the implementing module's directory unless
+ *     otherwise specified by the "file path" option. Does not apply to other
+ *     callbacks (only page callback).
+ *   - "file path": The path to the directory containing the file specified in
+ *     "file". This defaults to the path to the module implementing the hook.
+ *   - "load arguments": An array of arguments to be passed to each of the
+ *     wildcard object loaders in the path, after the path argument itself.
+ *     For example, if a module registers path node/%node/revisions/%/view
+ *     with load arguments set to array(3), the '%node' in the path indicates
+ *     that the loader function node_load() will be called with the second
+ *     path component as the first argument. The 3 in the load arguments
+ *     indicates that the fourth path component will also be passed to
+ *     node_load() (numbering of path components starts at zero). So, if path
+ *     node/12/revisions/29/view is requested, node_load(12, 29) will be called.
+ *     There are also two "magic" values that can be used in load arguments.
+ *     "%index" indicates the index of the wildcard path component. "%map"
+ *     indicates the path components as an array. For example, if a module
+ *     registers for several paths of the form 'user/%user_category/edit/*', all
+ *     of them can use the same load function user_category_load(), by setting
+ *     the load arguments to array('%map', '%index'). For instance, if the user
+ *     is editing category 'foo' by requesting path 'user/32/edit/foo', the load
+ *     function user_category_load() will be called with 32 as its first
+ *     argument, the array ('user', 32, 'edit', 'foo') as the map argument,
+ *     and 1 as the index argument (because %user_category is the second path
+ *     component and numbering starts at zero). user_category_load() can then
+ *     use these values to extract the information that 'foo' is the category
+ *     being requested.
+ *   - "weight": An integer that determines the relative position of items in
+ *     the menu; higher-weighted items sink. Defaults to 0. Menu items with the
+ *     same weight are ordered alphabetically.
+ *   - "menu_name": Optional. Set this to a custom menu if you don't want your
+ *     item to be placed in Navigation.
+ *   - "expanded": Optional. If set to TRUE, and if a menu link is provided for
+ *     this menu item (as a result of other properties), then the menu link is
+ *     always expanded, equivalent to its 'always expanded' checkbox being set
+ *     in the UI.
+ *   - "context": (optional) Defines the context a tab may appear in. By
+ *     default, all tabs are only displayed as local tasks when being rendered
+ *     in a page context. All tabs that should be accessible as contextual links
+ *     in page region containers outside of the parent menu item's primary page
+ *     context should be registered using one of the following contexts:
+ *     - MENU_CONTEXT_PAGE: (default) The tab is displayed as local task for the
+ *       page context only.
+ *     - MENU_CONTEXT_INLINE: The tab is displayed as contextual link outside of
+ *       the primary page context only.
+ *     Contexts can be combined. For example, to display a tab both on a page
+ *     and inline, a menu router item may specify:
+ *     @code
+ *       'context' => MENU_CONTEXT_PAGE | MENU_CONTEXT_INLINE,
+ *     @endcode
+ *   - "tab_parent": For local task menu items, the path of the task's parent
+ *     item; defaults to the same path without the last component (e.g., the
+ *     default parent for 'admin/people/create' is 'admin/people').
+ *   - "tab_root": For local task menu items, the path of the closest non-tab
+ *     item; same default as "tab_parent".
+ *   - "position": Position of the block ('left' or 'right') on the system
+ *     administration page for this item.
+ *   - "type": A bitmask of flags describing properties of the menu item.
+ *     Many shortcut bitmasks are provided as constants in menu.inc:
+ *     - MENU_NORMAL_ITEM: Normal menu items show up in the menu tree and can be
+ *       moved/hidden by the administrator.
+ *     - MENU_CALLBACK: Callbacks simply register a path so that the correct
+ *       information is generated when the path is accessed.
+ *     - MENU_SUGGESTED_ITEM: Modules may "suggest" menu items that the
+ *       administrator may enable.
+ *     - MENU_LOCAL_ACTION: Local actions are menu items that describe actions
+ *       on the parent item such as adding a new user or block, and are
+ *       rendered in the action-links list in your theme.
+ *     - MENU_LOCAL_TASK: Local tasks are menu items that describe different
+ *       displays of data, and are generally rendered as tabs.
+ *     - MENU_DEFAULT_LOCAL_TASK: Every set of local tasks should provide one
+ *       "default" task, which should display the same page as the parent item.
+ *     If the "type" element is omitted, MENU_NORMAL_ITEM is assumed.
+ *   - "options": An array of options to be passed to l() when generating a link
+ *     from this menu item. Note that the "options" parameter has no effect on
+ *     MENU_LOCAL_TASK, MENU_DEFAULT_LOCAL_TASK, and MENU_LOCAL_ACTION items.
+ *
+ * For a detailed usage example, see page_example.module.
+ * For comprehensive documentation on the menu system, see
+ * http://drupal.org/node/102338.
+ */
+function hook_menu() {
+  $items['example'] = array(
+    'title' => 'Example Page',
+    'page callback' => 'example_page',
+    'access arguments' => array('access content'),
+    'type' => MENU_SUGGESTED_ITEM,
+  );
+  $items['example/feed'] = array(
+    'title' => 'Example RSS feed',
+    'page callback' => 'example_feed',
+    'access arguments' => array('access content'),
+    'type' => MENU_CALLBACK,
+  );
+
+  return $items;
+}
+
+/**
+ * Alter the data being saved to the {menu_router} table after hook_menu is invoked.
+ *
+ * This hook is invoked by menu_router_build(). The menu definitions are passed
+ * in by reference. Each element of the $items array is one item returned
+ * by a module from hook_menu. Additional items may be added, or existing items
+ * altered.
+ *
+ * @param $items
+ *   Associative array of menu router definitions returned from hook_menu().
+ */
+function hook_menu_alter(&$items) {
+  // Example - disable the page at node/add
+  $items['node/add']['access callback'] = FALSE;
+}
+
+/**
+ * Alter the data being saved to the {menu_links} table by menu_link_save().
+ *
+ * @param $item
+ *   Associative array defining a menu link as passed into menu_link_save().
+ *
+ * @see hook_translated_menu_link_alter()
+ */
+function hook_menu_link_alter(&$item) {
+  // Make all new admin links hidden (a.k.a disabled).
+  if (strpos($item['link_path'], 'admin') === 0 && empty($item['mlid'])) {
+    $item['hidden'] = 1;
+  }
+  // Flag a link to be altered by hook_translated_menu_link_alter().
+  if ($item['link_path'] == 'devel/cache/clear') {
+    $item['options']['alter'] = TRUE;
+  }
+  // Flag a link to be altered by hook_translated_menu_link_alter(), but only
+  // if it is derived from a menu router item; i.e., do not alter a custom
+  // menu link pointing to the same path that has been created by a user.
+  if ($item['link_path'] == 'user' && $item['module'] == 'system') {
+    $item['options']['alter'] = TRUE;
+  }
+}
+
+/**
+ * Alter a menu link after it has been translated and before it is rendered.
+ *
+ * This hook is invoked from _menu_link_translate() after a menu link has been
+ * translated; i.e., after dynamic path argument placeholders (%) have been
+ * replaced with actual values, the user access to the link's target page has
+ * been checked, and the link has been localized. It is only invoked if
+ * $item['options']['alter'] has been set to a non-empty value (e.g., TRUE).
+ * This flag should be set using hook_menu_link_alter().
+ *
+ * Implementations of this hook are able to alter any property of the menu link.
+ * For example, this hook may be used to add a page-specific query string to all
+ * menu links, or hide a certain link by setting:
+ * @code
+ *   'hidden' => 1,
+ * @endcode
+ *
+ * @param $item
+ *   Associative array defining a menu link after _menu_link_translate()
+ * @param $map
+ *   Associative array containing the menu $map (path parts and/or objects).
+ *
+ * @see hook_menu_link_alter()
+ */
+function hook_translated_menu_link_alter(&$item, $map) {
+  if ($item['href'] == 'devel/cache/clear') {
+    $item['localized_options']['query'] = drupal_get_destination();
+  }
+}
+
+/**
+ * Inform modules that a menu link has been created.
+ *
+ * This hook is used to notify modules that menu items have been
+ * created. Contributed modules may use the information to perform
+ * actions based on the information entered into the menu system.
+ *
+ * @param $link
+ *   Associative array defining a menu link as passed into menu_link_save().
+ *
+ * @see hook_menu_link_update()
+ * @see hook_menu_link_delete()
+ */
+function hook_menu_link_insert($link) {
+  // In our sample case, we track menu items as editing sections
+  // of the site. These are stored in our table as 'disabled' items.
+  $record['mlid'] = $link['mlid'];
+  $record['menu_name'] = $link['menu_name'];
+  $record['status'] = 0;
+  drupal_write_record('menu_example', $record);
+}
+
+/**
+ * Inform modules that a menu link has been updated.
+ *
+ * This hook is used to notify modules that menu items have been
+ * updated. Contributed modules may use the information to perform
+ * actions based on the information entered into the menu system.
+ *
+ * @param $link
+ *   Associative array defining a menu link as passed into menu_link_save().
+ *
+ * @see hook_menu_link_insert()
+ * @see hook_menu_link_delete()
+ */
+function hook_menu_link_update($link) {
+  // If the parent menu has changed, update our record.
+  $menu_name = db_query("SELECT menu_name FROM {menu_example} WHERE mlid = :mlid", array(':mlid' => $link['mlid']))->fetchField();
+  if ($menu_name != $link['menu_name']) {
+    db_update('menu_example')
+      ->fields(array('menu_name' => $link['menu_name']))
+      ->condition('mlid', $link['mlid'])
+      ->execute();
+  }
+}
+
+/**
+ * Inform modules that a menu link has been deleted.
+ *
+ * This hook is used to notify modules that menu items have been
+ * deleted. Contributed modules may use the information to perform
+ * actions based on the information entered into the menu system.
+ *
+ * @param $link
+ *   Associative array defining a menu link as passed into menu_link_save().
+ *
+ * @see hook_menu_link_insert()
+ * @see hook_menu_link_update()
+ */
+function hook_menu_link_delete($link) {
+  // Delete the record from our table.
+  db_delete('menu_example')
+    ->condition('mlid', $link['mlid'])
+    ->execute();
+}
+
+/**
+ * Alter tabs and actions displayed on the page before they are rendered.
+ *
+ * This hook is invoked by menu_local_tasks(). The system-determined tabs and
+ * actions are passed in by reference. Additional tabs or actions may be added,
+ * or existing items altered.
+ *
+ * Each tab or action is an associative array containing:
+ * - #theme: The theme function to use to render.
+ * - #link: An associative array containing:
+ *   - title: The localized title of the link.
+ *   - href: The system path to link to.
+ *   - localized_options: An array of options to pass to l().
+ * - #active: Whether the link should be marked as 'active'.
+ *
+ * @param $data
+ *   An associative array containing:
+ *   - actions: An associative array containing:
+ *     - count: The amount of actions determined by the menu system, which can
+ *       be ignored.
+ *     - output: A list of of actions, each one being an associative array
+ *       as described above.
+ *   - tabs: An indexed array (list) of tab levels (up to 2 levels), each
+ *     containing an associative array:
+ *     - count: The amount of tabs determined by the menu system. This value
+ *       does not need to be altered if there is more than one tab.
+ *     - output: A list of of tabs, each one being an associative array as
+ *       described above.
+ * @param $router_item
+ *   The menu system router item of the page.
+ * @param $root_path
+ *   The path to the root item for this set of tabs.
+ */
+function hook_menu_local_tasks_alter(&$data, $router_item, $root_path) {
+  // Add an action linking to node/add to all pages.
+  $data['actions']['output'][] = array(
+    '#theme' => 'menu_local_task',
+    '#link' => array(
+      'title' => t('Add new content'),
+      'href' => 'node/add',
+      'localized_options' => array(
+        'attributes' => array(
+          'title' => t('Add new content'),
+        ),
+      ),
+    ),
+  );
+
+  // Add a tab linking to node/add to all pages.
+  $data['tabs'][0]['output'][] = array(
+    '#theme' => 'menu_local_task',
+    '#link' => array(
+      'title' => t('Example tab'),
+      'href' => 'node/add',
+      'localized_options' => array(
+        'attributes' => array(
+          'title' => t('Add new content'),
+        ),
+      ),
+    ),
+    // Define whether this link is active. This can be omitted for
+    // implementations that add links to pages outside of the current page
+    // context.
+    '#active' => ($router_item['path'] == $root_path),
+  );
+}
+
+/**
+ * Alter links in the active trail before it is rendered as the breadcrumb.
+ *
+ * This hook is invoked by menu_get_active_breadcrumb() and allows alteration
+ * of the breadcrumb links for the current page, which may be preferred instead
+ * of setting a custom breadcrumb via drupal_set_breadcrumb().
+ *
+ * Implementations should take into account that menu_get_active_breadcrumb()
+ * subsequently performs the following adjustments to the active trail *after*
+ * this hook has been invoked:
+ * - The last link in $active_trail is removed, if its 'href' is identical to
+ *   the 'href' of $item. This happens, because the breadcrumb normally does
+ *   not contain a link to the current page.
+ * - The (second to) last link in $active_trail is removed, if the current $item
+ *   is a MENU_DEFAULT_LOCAL_TASK. This happens in order to do not show a link
+ *   to the current page, when being on the path for the default local task;
+ *   e.g. when being on the path node/%/view, the breadcrumb should not contain
+ *   a link to node/%.
+ *
+ * Each link in the active trail must contain:
+ * - title: The localized title of the link.
+ * - href: The system path to link to.
+ * - localized_options: An array of options to pass to url().
+ *
+ * @param $active_trail
+ *   An array containing breadcrumb links for the current page.
+ * @param $item
+ *   The menu router item of the current page.
+ *
+ * @see drupal_set_breadcrumb()
+ * @see menu_get_active_breadcrumb()
+ * @see menu_get_active_trail()
+ * @see menu_set_active_trail()
+ */
+function hook_menu_breadcrumb_alter(&$active_trail, $item) {
+  // Always display a link to the current page by duplicating the last link in
+  // the active trail. This means that menu_get_active_breadcrumb() will remove
+  // the last link (for the current page), but since it is added once more here,
+  // it will appear.
+  if (!drupal_is_front_page()) {
+    $end = end($active_trail);
+    if ($item['href'] == $end['href']) {
+      $active_trail[] = $end;
+    }
+  }
+}
+
+/**
+ * Alter contextual links before they are rendered.
+ *
+ * This hook is invoked by menu_contextual_links(). The system-determined
+ * contextual links are passed in by reference. Additional links may be added
+ * or existing links can be altered.
+ *
+ * Each contextual link must at least contain:
+ * - title: The localized title of the link.
+ * - href: The system path to link to.
+ * - localized_options: An array of options to pass to url().
+ *
+ * @param $links
+ *   An associative array containing contextual links for the given $root_path,
+ *   as described above. The array keys are used to build CSS class names for
+ *   contextual links and must therefore be unique for each set of contextual
+ *   links.
+ * @param $router_item
+ *   The menu router item belonging to the $root_path being requested.
+ * @param $root_path
+ *   The (parent) path that has been requested to build contextual links for.
+ *   This is a normalized path, which means that an originally passed path of
+ *   'node/123' became 'node/%'.
+ *
+ * @see hook_contextual_links_view_alter()
+ * @see menu_contextual_links()
+ * @see hook_menu()
+ * @see contextual_preprocess()
+ */
+function hook_menu_contextual_links_alter(&$links, $router_item, $root_path) {
+  // Add a link to all contextual links for nodes.
+  if ($root_path == 'node/%') {
+    $links['foo'] = array(
+      'title' => t('Do fu'),
+      'href' => 'foo/do',
+      'localized_options' => array(
+        'query' => array(
+          'foo' => 'bar',
+        ),
+      ),
+    );
+  }
+}
+
+/**
+ * Perform alterations before a page is rendered.
+ *
+ * Use this hook when you want to remove or alter elements at the page
+ * level, or add elements at the page level that depend on an other module's
+ * elements (this hook runs after hook_page_build().
+ *
+ * If you are making changes to entities such as forms, menus, or user
+ * profiles, use those objects' native alter hooks instead (hook_form_alter(),
+ * for example).
+ *
+ * The $page array contains top level elements for each block region:
+ * @code
+ *   $page['page_top']
+ *   $page['header']
+ *   $page['sidebar_first']
+ *   $page['content']
+ *   $page['sidebar_second']
+ *   $page['page_bottom']
+ * @endcode
+ *
+ * The 'content' element contains the main content of the current page, and its
+ * structure will vary depending on what module is responsible for building the
+ * page. Some legacy modules may not return structured content at all: their
+ * pre-rendered markup will be located in $page['content']['main']['#markup'].
+ *
+ * Pages built by Drupal's core Node and Blog modules use a standard structure:
+ *
+ * @code
+ *   // Node body.
+ *   $page['content']['system_main']['nodes'][$nid]['body']
+ *   // Array of links attached to the node (add comments, read more).
+ *   $page['content']['system_main']['nodes'][$nid]['links']
+ *   // The node object itself.
+ *   $page['content']['system_main']['nodes'][$nid]['#node']
+ *   // The results pager.
+ *   $page['content']['system_main']['pager']
+ * @endcode
+ *
+ * Blocks may be referenced by their module/delta pair within a region:
+ * @code
+ *   // The login block in the first sidebar region.
+ *   $page['sidebar_first']['user_login']['#block'];
+ * @endcode
+ *
+ * @param $page
+ *   Nested array of renderable elements that make up the page.
+ *
+ * @see hook_page_build()
+ * @see drupal_render_page()
+ */
+function hook_page_alter(&$page) {
+  // Add help text to the user login block.
+  $page['sidebar_first']['user_login']['help'] = array(
+    '#weight' => -10,
+    '#markup' => t('To post comments or add new content, you first have to log in.'),
+  );
+}
+
+/**
+ * Perform alterations before a form is rendered.
+ *
+ * One popular use of this hook is to add form elements to the node form. When
+ * altering a node form, the node object can be accessed at $form['#node'].
+ *
+ * In addition to hook_form_alter(), which is called for all forms, there are
+ * two more specific form hooks available. The first,
+ * hook_form_BASE_FORM_ID_alter(), allows targeting of a form/forms via a base
+ * form (if one exists). The second, hook_form_FORM_ID_alter(), can be used to
+ * target a specific form directly.
+ *
+ * The call order is as follows: all existing form alter functions are called
+ * for module A, then all for module B, etc., followed by all for any base
+ * theme(s), and finally for the theme itself. The module order is determined
+ * by system weight, then by module name.
+ *
+ * Within each module, form alter hooks are called in the following order:
+ * first, hook_form_alter(); second, hook_form_BASE_FORM_ID_alter(); third,
+ * hook_form_FORM_ID_alter(). So, for each module, the more general hooks are
+ * called first followed by the more specific.
+ *
+ * @param $form
+ *   Nested array of form elements that comprise the form.
+ * @param $form_state
+ *   A keyed array containing the current state of the form. The arguments
+ *   that drupal_get_form() was originally called with are available in the
+ *   array $form_state['build_info']['args'].
+ * @param $form_id
+ *   String representing the name of the form itself. Typically this is the
+ *   name of the function that generated the form.
+ *
+ * @see hook_form_BASE_FORM_ID_alter()
+ * @see hook_form_FORM_ID_alter()
+ * @see forms_api_reference.html
+ */
+function hook_form_alter(&$form, &$form_state, $form_id) {
+  if (isset($form['type']) && $form['type']['#value'] . '_node_settings' == $form_id) {
+    $form['workflow']['upload_' . $form['type']['#value']] = array(
+      '#type' => 'radios',
+      '#title' => t('Attachments'),
+      '#default_value' => variable_get('upload_' . $form['type']['#value'], 1),
+      '#options' => array(t('Disabled'), t('Enabled')),
+    );
+  }
+}
+
+/**
+ * Provide a form-specific alteration instead of the global hook_form_alter().
+ *
+ * Modules can implement hook_form_FORM_ID_alter() to modify a specific form,
+ * rather than implementing hook_form_alter() and checking the form ID, or
+ * using long switch statements to alter multiple forms.
+ *
+ * Form alter hooks are called in the following order: hook_form_alter(),
+ * hook_form_BASE_FORM_ID_alter(), hook_form_FORM_ID_alter(). See
+ * hook_form_alter() for more details.
+ *
+ * @param $form
+ *   Nested array of form elements that comprise the form.
+ * @param $form_state
+ *   A keyed array containing the current state of the form. The arguments
+ *   that drupal_get_form() was originally called with are available in the
+ *   array $form_state['build_info']['args'].
+ * @param $form_id
+ *   String representing the name of the form itself. Typically this is the
+ *   name of the function that generated the form.
+ *
+ * @see hook_form_alter()
+ * @see hook_form_BASE_FORM_ID_alter()
+ * @see drupal_prepare_form()
+ * @see forms_api_reference.html
+ */
+function hook_form_FORM_ID_alter(&$form, &$form_state, $form_id) {
+  // Modification for the form with the given form ID goes here. For example, if
+  // FORM_ID is "user_register_form" this code would run only on the user
+  // registration form.
+
+  // Add a checkbox to registration form about agreeing to terms of use.
+  $form['terms_of_use'] = array(
+    '#type' => 'checkbox',
+    '#title' => t("I agree with the website's terms and conditions."),
+    '#required' => TRUE,
+  );
+}
+
+/**
+ * Provide a form-specific alteration for shared ('base') forms.
+ *
+ * By default, when drupal_get_form() is called, Drupal looks for a function
+ * with the same name as the form ID, and uses that function to build the form.
+ * In contrast, base forms allow multiple form IDs to be mapped to a single base
+ * (also called 'factory') form function.
+ *
+ * Modules can implement hook_form_BASE_FORM_ID_alter() to modify a specific
+ * base form, rather than implementing hook_form_alter() and checking for
+ * conditions that would identify the shared form constructor.
+ *
+ * To identify the base form ID for a particular form (or to determine whether
+ * one exists) check the $form_state. The base form ID is stored under
+ * $form_state['build_info']['base_form_id'].
+ *
+ * See hook_forms() for more information on how to implement base forms in
+ * Drupal.
+ *
+ * Form alter hooks are called in the following order: hook_form_alter(),
+ * hook_form_BASE_FORM_ID_alter(), hook_form_FORM_ID_alter(). See
+ * hook_form_alter() for more details.
+ *
+ * @param $form
+ *   Nested array of form elements that comprise the form.
+ * @param $form_state
+ *   A keyed array containing the current state of the form.
+ * @param $form_id
+ *   String representing the name of the form itself. Typically this is the
+ *   name of the function that generated the form.
+ *
+ * @see hook_form_alter()
+ * @see hook_form_FORM_ID_alter()
+ * @see drupal_prepare_form()
+ * @see hook_forms()
+ */
+function hook_form_BASE_FORM_ID_alter(&$form, &$form_state, $form_id) {
+  // Modification for the form with the given BASE_FORM_ID goes here. For
+  // example, if BASE_FORM_ID is "node_form", this code would run on every
+  // node form, regardless of node type.
+
+  // Add a checkbox to the node form about agreeing to terms of use.
+  $form['terms_of_use'] = array(
+    '#type' => 'checkbox',
+    '#title' => t("I agree with the website's terms and conditions."),
+    '#required' => TRUE,
+  );
+}
+
+/**
+ * Map form_ids to form builder functions.
+ *
+ * By default, when drupal_get_form() is called, the system will look for a
+ * function with the same name as the form ID, and use that function to build
+ * the form. If no such function is found, Drupal calls this hook. Modules
+ * implementing this hook can then provide their own instructions for mapping
+ * form IDs to constructor functions. As a result, you can easily map multiple
+ * form IDs to a single form constructor (referred to as a 'base' form).
+ *
+ * Using a base form can help to avoid code duplication, by allowing many
+ * similar forms to use the same code base. Another benefit is that it becomes
+ * much easier for other modules to apply a general change to the group of
+ * forms; hook_form_BASE_FORM_ID_alter() can be used to easily alter multiple
+ * forms at once by directly targeting the shared base form.
+ *
+ * Two example use cases where base forms may be useful are given below.
+ *
+ * First, you can use this hook to tell the form system to use a different
+ * function to build certain forms in your module; this is often used to define
+ * a form "factory" function that is used to build several similar forms. In
+ * this case, your hook implementation will likely ignore all of the input
+ * arguments. See node_forms() for an example of this. Note, node_forms() is the
+ * hook_forms() implementation; the base form itself is defined in node_form().
+ *
+ * Second, you could use this hook to define how to build a form with a
+ * dynamically-generated form ID. In this case, you would need to verify that
+ * the $form_id input matched your module's format for dynamically-generated
+ * form IDs, and if so, act appropriately.
+ *
+ * @param $form_id
+ *   The unique string identifying the desired form.
+ * @param $args
+ *   An array containing the original arguments provided to drupal_get_form()
+ *   or drupal_form_submit(). These are always passed to the form builder and
+ *   do not have to be specified manually in 'callback arguments'.
+ *
+ * @return
+ *   An associative array whose keys define form_ids and whose values are an
+ *   associative array defining the following keys:
+ *   - callback: The name of the form builder function to invoke. This will be
+ *     used for the base form ID, for example, to target a base form using
+ *     hook_form_BASE_FORM_ID_alter().
+ *   - callback arguments: (optional) Additional arguments to pass to the
+ *     function defined in 'callback', which are prepended to $args.
+ *   - wrapper_callback: (optional) The name of a form builder function to
+ *     invoke before the form builder defined in 'callback' is invoked. This
+ *     wrapper callback may prepopulate the $form array with form elements,
+ *     which will then be already contained in the $form that is passed on to
+ *     the form builder defined in 'callback'. For example, a wrapper callback
+ *     could setup wizard-alike form buttons that are the same for a variety of
+ *     forms that belong to the wizard, which all share the same wrapper
+ *     callback.
+ */
+function hook_forms($form_id, $args) {
+  // Simply reroute the (non-existing) $form_id 'mymodule_first_form' to
+  // 'mymodule_main_form'.
+  $forms['mymodule_first_form'] = array(
+    'callback' => 'mymodule_main_form',
+  );
+
+  // Reroute the $form_id and prepend an additional argument that gets passed to
+  // the 'mymodule_main_form' form builder function.
+  $forms['mymodule_second_form'] = array(
+    'callback' => 'mymodule_main_form',
+    'callback arguments' => array('some parameter'),
+  );
+
+  // Reroute the $form_id, but invoke the form builder function
+  // 'mymodule_main_form_wrapper' first, so we can prepopulate the $form array
+  // that is passed to the actual form builder 'mymodule_main_form'.
+  $forms['mymodule_wrapped_form'] = array(
+    'callback' => 'mymodule_main_form',
+    'wrapper_callback' => 'mymodule_main_form_wrapper',
+  );
+
+  return $forms;
+}
+
+/**
+ * Perform setup tasks for all page requests.
+ *
+ * This hook is run at the beginning of the page request. It is typically
+ * used to set up global parameters that are needed later in the request.
+ *
+ * Only use this hook if your code must run even for cached page views. This
+ * hook is called before the theme, modules, or most include files are loaded
+ * into memory. It happens while Drupal is still in bootstrap mode.
+ *
+ * @see hook_init()
+ */
+function hook_boot() {
+  // We need user_access() in the shutdown function. Make sure it gets loaded.
+  drupal_load('module', 'user');
+  drupal_register_shutdown_function('devel_shutdown');
+}
+
+/**
+ * Perform setup tasks for non-cached page requests.
+ *
+ * This hook is run at the beginning of the page request. It is typically
+ * used to set up global parameters that are needed later in the request.
+ * When this hook is called, the theme and all modules are already loaded in
+ * memory.
+ *
+ * This hook is not run on cached pages.
+ *
+ * To add CSS or JS that should be present on all pages, modules should not
+ * implement this hook, but declare these files in their .info file.
+ *
+ * @see hook_boot()
+ */
+function hook_init() {
+  // Since this file should only be loaded on the front page, it cannot be
+  // declared in the info file.
+  if (drupal_is_front_page()) {
+    drupal_add_css(drupal_get_path('module', 'foo') . '/foo.css');
+  }
+}
+
+/**
+ * Define image toolkits provided by this module.
+ *
+ * The file which includes each toolkit's functions must be declared as part of
+ * the files array in the module .info file so that the registry will find and
+ * parse it.
+ *
+ * The toolkit's functions must be named image_toolkitname_operation().
+ * where the operation may be:
+ *   - 'load': Required. See image_gd_load() for usage.
+ *   - 'save': Required. See image_gd_save() for usage.
+ *   - 'settings': Optional. See image_gd_settings() for usage.
+ *   - 'resize': Optional. See image_gd_resize() for usage.
+ *   - 'rotate': Optional. See image_gd_rotate() for usage.
+ *   - 'crop': Optional. See image_gd_crop() for usage.
+ *   - 'desaturate': Optional. See image_gd_desaturate() for usage.
+ *
+ * @return
+ *   An array with the toolkit name as keys and sub-arrays with these keys:
+ *     - 'title': A string with the toolkit's title.
+ *     - 'available': A Boolean value to indicate that the toolkit is operating
+ *       properly, e.g. all required libraries exist.
+ *
+ * @see system_image_toolkits()
+ */
+function hook_image_toolkits() {
+  return array(
+    'working' => array(
+      'title' => t('A toolkit that works.'),
+      'available' => TRUE,
+    ),
+    'broken' => array(
+      'title' => t('A toolkit that is "broken" and will not be listed.'),
+      'available' => FALSE,
+    ),
+  );
+}
+
+/**
+ * Alter an email message created with the drupal_mail() function.
+ *
+ * hook_mail_alter() allows modification of email messages created and sent
+ * with drupal_mail(). Usage examples include adding and/or changing message
+ * text, message fields, and message headers.
+ *
+ * Email messages sent using functions other than drupal_mail() will not
+ * invoke hook_mail_alter(). For example, a contributed module directly
+ * calling the drupal_mail_system()->mail() or PHP mail() function
+ * will not invoke this hook. All core modules use drupal_mail() for
+ * messaging, it is best practice but not mandatory in contributed modules.
+ *
+ * @param $message
+ *   An array containing the message data. Keys in this array include:
+ *  - 'id':
+ *     The drupal_mail() id of the message. Look at module source code or
+ *     drupal_mail() for possible id values.
+ *  - 'to':
+ *     The address or addresses the message will be sent to. The formatting of
+ *     this string will be validated with the
+ *     @link http://php.net/manual/filter.filters.validate.php PHP e-mail validation filter. @endlink
+ *  - 'from':
+ *     The address the message will be marked as being from, which is
+ *     either a custom address or the site-wide default email address.
+ *  - 'subject':
+ *     Subject of the email to be sent. This must not contain any newline
+ *     characters, or the email may not be sent properly.
+ *  - 'body':
+ *     An array of strings containing the message text. The message body is
+ *     created by concatenating the individual array strings into a single text
+ *     string using "\n\n" as a separator.
+ *  - 'headers':
+ *     Associative array containing mail headers, such as From, Sender,
+ *     MIME-Version, Content-Type, etc.
+ *  - 'params':
+ *     An array of optional parameters supplied by the caller of drupal_mail()
+ *     that is used to build the message before hook_mail_alter() is invoked.
+ *  - 'language':
+ *     The language object used to build the message before hook_mail_alter()
+ *     is invoked.
+ *  - 'send':
+ *     Set to FALSE to abort sending this email message.
+ *
+ * @see drupal_mail()
+ */
+function hook_mail_alter(&$message) {
+  if ($message['id'] == 'modulename_messagekey') {
+    if (!example_notifications_optin($message['to'], $message['id'])) {
+      // If the recipient has opted to not receive such messages, cancel
+      // sending.
+      $message['send'] = FALSE;
+      return;
+    }
+    $message['body'][] = "--\nMail sent out from " . variable_get('site_name', t('Drupal'));
+  }
+}
+
+/**
+ * Alter the registry of modules implementing a hook.
+ *
+ * This hook is invoked during module_implements(). A module may implement this
+ * hook in order to reorder the implementing modules, which are otherwise
+ * ordered by the module's system weight.
+ *
+ * Note that hooks invoked using drupal_alter() can have multiple variations
+ * (such as hook_form_alter() and hook_form_FORM_ID_alter()). drupal_alter()
+ * will call all such variants defined by a single module in turn. For the
+ * purposes of hook_module_implements_alter(), these variants are treated as
+ * a single hook. Thus, to ensure that your implementation of
+ * hook_form_FORM_ID_alter() is called at the right time, you will have to
+ * change the order of hook_form_alter() implementation in
+ * hook_module_implements_alter().
+ *
+ * @param $implementations
+ *   An array keyed by the module's name. The value of each item corresponds
+ *   to a $group, which is usually FALSE, unless the implementation is in a
+ *   file named $module.$group.inc.
+ * @param $hook
+ *   The name of the module hook being implemented.
+ */
+function hook_module_implements_alter(&$implementations, $hook) {
+  if ($hook == 'rdf_mapping') {
+    // Move my_module_rdf_mapping() to the end of the list. module_implements()
+    // iterates through $implementations with a foreach loop which PHP iterates
+    // in the order that the items were added, so to move an item to the end of
+    // the array, we remove it and then add it.
+    $group = $implementations['my_module'];
+    unset($implementations['my_module']);
+    $implementations['my_module'] = $group;
+  }
+}
+
+/**
+ * Return additional themes provided by modules.
+ *
+ * Only use this hook for testing purposes. Use a hidden MYMODULE_test.module
+ * to implement this hook. Testing themes should be hidden, too.
+ *
+ * This hook is invoked from _system_rebuild_theme_data() and allows modules to
+ * register additional themes outside of the regular 'themes' directories of a
+ * Drupal installation.
+ *
+ * @return
+ *   An associative array. Each key is the system name of a theme and each value
+ *   is the corresponding path to the theme's .info file.
+ */
+function hook_system_theme_info() {
+  $themes['mymodule_test_theme'] = drupal_get_path('module', 'mymodule') . '/mymodule_test_theme/mymodule_test_theme.info';
+  return $themes;
+}
+
+/**
+ * Alter the information parsed from module and theme .info files
+ *
+ * This hook is invoked in _system_rebuild_module_data() and in
+ * _system_rebuild_theme_data(). A module may implement this hook in order to
+ * add to or alter the data generated by reading the .info file with
+ * drupal_parse_info_file().
+ *
+ * @param $info
+ *   The .info file contents, passed by reference so that it can be altered.
+ * @param $file
+ *   Full information about the module or theme, including $file->name, and
+ *   $file->filename
+ * @param $type
+ *   Either 'module' or 'theme', depending on the type of .info file that was
+ *   passed.
+ */
+function hook_system_info_alter(&$info, $file, $type) {
+  // Only fill this in if the .info file does not define a 'datestamp'.
+  if (empty($info['datestamp'])) {
+    $info['datestamp'] = filemtime($file->filename);
+  }
+}
+
+/**
+ * Define user permissions.
+ *
+ * This hook can supply permissions that the module defines, so that they
+ * can be selected on the user permissions page and used to grant or restrict
+ * access to actions the module performs.
+ *
+ * Permissions are checked using user_access().
+ *
+ * For a detailed usage example, see page_example.module.
+ *
+ * @return
+ *   An array whose keys are permission names and whose corresponding values
+ *   are arrays containing the following key-value pairs:
+ *   - title: The human-readable name of the permission, to be shown on the
+ *     permission administration page. This should be wrapped in the t()
+ *     function so it can be translated.
+ *   - description: (optional) A description of what the permission does. This
+ *     should be wrapped in the t() function so it can be translated.
+ *   - restrict access: (optional) A boolean which can be set to TRUE to
+ *     indicate that site administrators should restrict access to this
+ *     permission to trusted users. This should be used for permissions that
+ *     have inherent security risks across a variety of potential use cases
+ *     (for example, the "administer filters" and "bypass node access"
+ *     permissions provided by Drupal core). When set to TRUE, a standard
+ *     warning message defined in user_admin_permissions() and output via
+ *     theme_user_permission_description() will be associated with the
+ *     permission and displayed with it on the permission administration page.
+ *     Defaults to FALSE.
+ *   - warning: (optional) A translated warning message to display for this
+ *     permission on the permission administration page. This warning overrides
+ *     the automatic warning generated by 'restrict access' being set to TRUE.
+ *     This should rarely be used, since it is important for all permissions to
+ *     have a clear, consistent security warning that is the same across the
+ *     site. Use the 'description' key instead to provide any information that
+ *     is specific to the permission you are defining.
+ *
+ * @see theme_user_permission_description()
+ */
+function hook_permission() {
+  return array(
+    'administer my module' =>  array(
+      'title' => t('Administer my module'),
+      'description' => t('Perform administration tasks for my module.'),
+    ),
+  );
+}
+
+/**
+ * Register a module (or theme's) theme implementations.
+ *
+ * The implementations declared by this hook have two purposes: either they
+ * specify how a particular render array is to be rendered as HTML (this is
+ * usually the case if the theme function is assigned to the render array's
+ * #theme property), or they return the HTML that should be returned by an
+ * invocation of theme(). See
+ * @link http://drupal.org/node/933976 Using the theme layer Drupal 7.x @endlink
+ * for more information on how to implement theme hooks.
+ *
+ * The following parameters are all optional.
+ *
+ * @param array $existing
+ *   An array of existing implementations that may be used for override
+ *   purposes. This is primarily useful for themes that may wish to examine
+ *   existing implementations to extract data (such as arguments) so that
+ *   it may properly register its own, higher priority implementations.
+ * @param $type
+ *   Whether a theme, module, etc. is being processed. This is primarily useful
+ *   so that themes tell if they are the actual theme being called or a parent
+ *   theme. May be one of:
+ *   - 'module': A module is being checked for theme implementations.
+ *   - 'base_theme_engine': A theme engine is being checked for a theme that is
+ *     a parent of the actual theme being used.
+ *   - 'theme_engine': A theme engine is being checked for the actual theme
+ *     being used.
+ *   - 'base_theme': A base theme is being checked for theme implementations.
+ *   - 'theme': The actual theme in use is being checked.
+ * @param $theme
+ *   The actual name of theme, module, etc. that is being being processed.
+ * @param $path
+ *   The directory path of the theme or module, so that it doesn't need to be
+ *   looked up.
+ *
+ * @return array
+ *   An associative array of theme hook information. The keys on the outer
+ *   array are the internal names of the hooks, and the values are arrays
+ *   containing information about the hook. Each information array must contain
+ *   either a 'variables' element or a 'render element' element, but not both.
+ *   Use 'render element' if you are theming a single element or element tree
+ *   composed of elements, such as a form array, a page array, or a single
+ *   checkbox element. Use 'variables' if your theme implementation is
+ *   intended to be called directly through theme() and has multiple arguments
+ *   for the data and style; in this case, the variables not supplied by the
+ *   calling function will be given default values and passed to the template
+ *   or theme function. The returned theme information array can contain the
+ *   following key/value pairs:
+ *   - variables: (see above) Each array key is the name of the variable, and
+ *     the value given is used as the default value if the function calling
+ *     theme() does not supply it. Template implementations receive each array
+ *     key as a variable in the template file (so they must be legal PHP
+ *     variable names). Function implementations are passed the variables in a
+ *     single $variables function argument.
+ *   - render element: (see above) The name of the renderable element or element
+ *     tree to pass to the theme function. This name is used as the name of the
+ *     variable that holds the renderable element or tree in preprocess and
+ *     process functions.
+ *   - file: The file the implementation resides in. This file will be included
+ *     prior to the theme being rendered, to make sure that the function or
+ *     preprocess function (as needed) is actually loaded; this makes it
+ *     possible to split theme functions out into separate files quite easily.
+ *   - path: Override the path of the file to be used. Ordinarily the module or
+ *     theme path will be used, but if the file will not be in the default
+ *     path, include it here. This path should be relative to the Drupal root
+ *     directory.
+ *   - template: If specified, this theme implementation is a template, and
+ *     this is the template file without an extension. Do not put .tpl.php on
+ *     this file; that extension will be added automatically by the default
+ *     rendering engine (which is PHPTemplate). If 'path', above, is specified,
+ *     the template should also be in this path.
+ *   - function: If specified, this will be the function name to invoke for
+ *     this implementation. If neither 'template' nor 'function' is specified,
+ *     a default function name will be assumed. For example, if a module
+ *     registers the 'node' theme hook, 'theme_node' will be assigned to its
+ *     function. If the chameleon theme registers the node hook, it will be
+ *     assigned 'chameleon_node' as its function.
+ *   - base hook: A string declaring the base theme hook if this theme
+ *     implementation is actually implementing a suggestion for another theme
+ *     hook.
+ *   - pattern: A regular expression pattern to be used to allow this theme
+ *     implementation to have a dynamic name. The convention is to use __ to
+ *     differentiate the dynamic portion of the theme. For example, to allow
+ *     forums to be themed individually, the pattern might be: 'forum__'. Then,
+ *     when the forum is themed, call:
+ *     @code
+ *     theme(array('forum__' . $tid, 'forum'), $forum)
+ *     @endcode
+ *   - preprocess functions: A list of functions used to preprocess this data.
+ *     Ordinarily this won't be used; it's automatically filled in. By default,
+ *     for a module this will be filled in as template_preprocess_HOOK. For
+ *     a theme this will be filled in as phptemplate_preprocess and
+ *     phptemplate_preprocess_HOOK as well as themename_preprocess and
+ *     themename_preprocess_HOOK.
+ *   - override preprocess functions: Set to TRUE when a theme does NOT want
+ *     the standard preprocess functions to run. This can be used to give a
+ *     theme FULL control over how variables are set. For example, if a theme
+ *     wants total control over how certain variables in the page.tpl.php are
+ *     set, this can be set to true. Please keep in mind that when this is used
+ *     by a theme, that theme becomes responsible for making sure necessary
+ *     variables are set.
+ *   - type: (automatically derived) Where the theme hook is defined:
+ *     'module', 'theme_engine', or 'theme'.
+ *   - theme path: (automatically derived) The directory path of the theme or
+ *     module, so that it doesn't need to be looked up.
+ *
+ * @see hook_theme_registry_alter()
+ */
+function hook_theme($existing, $type, $theme, $path) {
+  return array(
+    'forum_display' => array(
+      'variables' => array('forums' => NULL, 'topics' => NULL, 'parents' => NULL, 'tid' => NULL, 'sortby' => NULL, 'forum_per_page' => NULL),
+    ),
+    'forum_list' => array(
+      'variables' => array('forums' => NULL, 'parents' => NULL, 'tid' => NULL),
+    ),
+    'forum_topic_list' => array(
+      'variables' => array('tid' => NULL, 'topics' => NULL, 'sortby' => NULL, 'forum_per_page' => NULL),
+    ),
+    'forum_icon' => array(
+      'variables' => array('new_posts' => NULL, 'num_posts' => 0, 'comment_mode' => 0, 'sticky' => 0),
+    ),
+    'status_report' => array(
+      'render element' => 'requirements',
+      'file' => 'system.admin.inc',
+    ),
+    'system_date_time_settings' => array(
+      'render element' => 'form',
+      'file' => 'system.admin.inc',
+    ),
+  );
+}
+
+/**
+ * Alter the theme registry information returned from hook_theme().
+ *
+ * The theme registry stores information about all available theme hooks,
+ * including which callback functions those hooks will call when triggered,
+ * what template files are exposed by these hooks, and so on.
+ *
+ * Note that this hook is only executed as the theme cache is re-built.
+ * Changes here will not be visible until the next cache clear.
+ *
+ * The $theme_registry array is keyed by theme hook name, and contains the
+ * information returned from hook_theme(), as well as additional properties
+ * added by _theme_process_registry().
+ *
+ * For example:
+ * @code
+ * $theme_registry['user_profile'] = array(
+ *   'variables' => array(
+ *     'account' => NULL,
+ *   ),
+ *   'template' => 'modules/user/user-profile',
+ *   'file' => 'modules/user/user.pages.inc',
+ *   'type' => 'module',
+ *   'theme path' => 'modules/user',
+ *   'preprocess functions' => array(
+ *     0 => 'template_preprocess',
+ *     1 => 'template_preprocess_user_profile',
+ *   ),
+ * );
+ * @endcode
+ *
+ * @param $theme_registry
+ *   The entire cache of theme registry information, post-processing.
+ *
+ * @see hook_theme()
+ * @see _theme_process_registry()
+ */
+function hook_theme_registry_alter(&$theme_registry) {
+  // Kill the next/previous forum topic navigation links.
+  foreach ($theme_registry['forum_topic_navigation']['preprocess functions'] as $key => $value) {
+    if ($value == 'template_preprocess_forum_topic_navigation') {
+      unset($theme_registry['forum_topic_navigation']['preprocess functions'][$key]);
+    }
+  }
+}
+
+/**
+ * Return the machine-readable name of the theme to use for the current page.
+ *
+ * This hook can be used to dynamically set the theme for the current page
+ * request. It should be used by modules which need to override the theme
+ * based on dynamic conditions (for example, a module which allows the theme to
+ * be set based on the current user's role). The return value of this hook will
+ * be used on all pages except those which have a valid per-page or per-section
+ * theme set via a theme callback function in hook_menu(); the themes on those
+ * pages can only be overridden using hook_menu_alter().
+ *
+ * Note that returning different themes for the same path may not work with page
+ * caching. This is most likely to be a problem if an anonymous user on a given
+ * path could have different themes returned under different conditions.
+ *
+ * Since only one theme can be used at a time, the last (i.e., highest
+ * weighted) module which returns a valid theme name from this hook will
+ * prevail.
+ *
+ * @return
+ *   The machine-readable name of the theme that should be used for the current
+ *   page request. The value returned from this function will only have an
+ *   effect if it corresponds to a currently-active theme on the site. Do not
+ *   return a value if you do not wish to set a custom theme.
+ */
+function hook_custom_theme() {
+  // Allow the user to request a particular theme via a query parameter.
+  if (isset($_GET['theme'])) {
+    return $_GET['theme'];
+  }
+}
+
+/**
+ * Register XML-RPC callbacks.
+ *
+ * This hook lets a module register callback functions to be called when
+ * particular XML-RPC methods are invoked by a client.
+ *
+ * @return
+ *   An array which maps XML-RPC methods to Drupal functions. Each array
+ *   element is either a pair of method => function or an array with four
+ *   entries:
+ *   - The XML-RPC method name (for example, module.function).
+ *   - The Drupal callback function (for example, module_function).
+ *   - The method signature is an array of XML-RPC types. The first element
+ *     of this array is the type of return value and then you should write a
+ *     list of the types of the parameters. XML-RPC types are the following
+ *     (See the types at http://www.xmlrpc.com/spec):
+ *       - "boolean": 0 (false) or 1 (true).
+ *       - "double": a floating point number (for example, -12.214).
+ *       - "int": a integer number (for example,  -12).
+ *       - "array": an array without keys (for example, array(1, 2, 3)).
+ *       - "struct": an associative array or an object (for example,
+ *          array('one' => 1, 'two' => 2)).
+ *       - "date": when you return a date, then you may either return a
+ *          timestamp (time(), mktime() etc.) or an ISO8601 timestamp. When
+ *          date is specified as an input parameter, then you get an object,
+ *          which is described in the function xmlrpc_date
+ *       - "base64": a string containing binary data, automatically
+ *          encoded/decoded automatically.
+ *       - "string": anything else, typically a string.
+ *   - A descriptive help string, enclosed in a t() function for translation
+ *     purposes.
+ *   Both forms are shown in the example.
+ */
+function hook_xmlrpc() {
+  return array(
+    'drupal.login' => 'drupal_login',
+    array(
+      'drupal.site.ping',
+      'drupal_directory_ping',
+      array('boolean', 'string', 'string', 'string', 'string', 'string'),
+      t('Handling ping request'))
+  );
+}
+
+/**
+ * Alters the definition of XML-RPC methods before they are called.
+ *
+ * This hook allows modules to modify the callback definition of declared
+ * XML-RPC methods, right before they are invoked by a client. Methods may be
+ * added, or existing methods may be altered.
+ *
+ * Note that hook_xmlrpc() supports two distinct and incompatible formats to
+ * define a callback, so care must be taken when altering other methods.
+ *
+ * @param $methods
+ *   An asssociative array of method callback definitions, as returned from
+ *   hook_xmlrpc() implementations.
+ *
+ * @see hook_xmlrpc()
+ * @see xmlrpc_server()
+ */
+function hook_xmlrpc_alter(&$methods) {
+  // Directly change a simple method.
+  $methods['drupal.login'] = 'mymodule_login';
+
+  // Alter complex definitions.
+  foreach ($methods as $key => &$method) {
+    // Skip simple method definitions.
+    if (!is_int($key)) {
+      continue;
+    }
+    // Perform the wanted manipulation.
+    if ($method[0] == 'drupal.site.ping') {
+      $method[1] = 'mymodule_directory_ping';
+    }
+  }
+}
+
+/**
+ * Log an event message.
+ *
+ * This hook allows modules to route log events to custom destinations, such as
+ * SMS, Email, pager, syslog, ...etc.
+ *
+ * @param $log_entry
+ *   An associative array containing the following keys:
+ *   - type: The type of message for this entry.
+ *   - user: The user object for the user who was logged in when the event
+ *     happened.
+ *   - uid: The user ID for the user who was logged in when the event happened.
+ *   - request_uri: The request URI for the page the event happened in.
+ *   - referer: The page that referred the user to the page where the event
+ *     occurred.
+ *   - ip: The IP address where the request for the page came from.
+ *   - timestamp: The UNIX timestamp of the date/time the event occurred.
+ *   - severity: The severity of the message; one of the following values as
+ *     defined in @link http://www.faqs.org/rfcs/rfc3164.html RFC 3164: @endlink
+ *     - WATCHDOG_EMERGENCY: Emergency, system is unusable.
+ *     - WATCHDOG_ALERT: Alert, action must be taken immediately.
+ *     - WATCHDOG_CRITICAL: Critical conditions.
+ *     - WATCHDOG_ERROR: Error conditions.
+ *     - WATCHDOG_WARNING: Warning conditions.
+ *     - WATCHDOG_NOTICE: Normal but significant conditions.
+ *     - WATCHDOG_INFO: Informational messages.
+ *     - WATCHDOG_DEBUG: Debug-level messages.
+ *   - link: An optional link provided by the module that called the watchdog()
+ *     function.
+ *   - message: The text of the message to be logged. Variables in the message
+ *     are indicated by using placeholder strings alongside the variables
+ *     argument to declare the value of the placeholders. See t() for
+ *     documentation on how the message and variable parameters interact.
+ *   - variables: An array of variables to be inserted into the message on
+ *     display. Will be NULL or missing if a message is already translated or if
+ *     the message is not possible to translate.
+ */
+function hook_watchdog(array $log_entry) {
+  global $base_url, $language;
+
+  $severity_list = array(
+    WATCHDOG_EMERGENCY => t('Emergency'),
+    WATCHDOG_ALERT     => t('Alert'),
+    WATCHDOG_CRITICAL  => t('Critical'),
+    WATCHDOG_ERROR     => t('Error'),
+    WATCHDOG_WARNING   => t('Warning'),
+    WATCHDOG_NOTICE    => t('Notice'),
+    WATCHDOG_INFO      => t('Info'),
+    WATCHDOG_DEBUG     => t('Debug'),
+  );
+
+  $to = '[e-mail]';
+  $params = array();
+  $params['subject'] = t('[@site_name] @severity_desc: Alert from your web site', array(
+    '@site_name' => variable_get('site_name', 'Drupal'),
+    '@severity_desc' => $severity_list[$log_entry['severity']],
+  ));
+
+  $params['message']  = "\nSite:         @base_url";
+  $params['message'] .= "\nSeverity:     (@severity) @severity_desc";
+  $params['message'] .= "\nTimestamp:    @timestamp";
+  $params['message'] .= "\nType:         @type";
+  $params['message'] .= "\nIP Address:   @ip";
+  $params['message'] .= "\nRequest URI:  @request_uri";
+  $params['message'] .= "\nReferrer URI: @referer_uri";
+  $params['message'] .= "\nUser:         (@uid) @name";
+  $params['message'] .= "\nLink:         @link";
+  $params['message'] .= "\nMessage:      \n\n@message";
+
+  $params['message'] = t($params['message'], array(
+    '@base_url'      => $base_url,
+    '@severity'      => $log_entry['severity'],
+    '@severity_desc' => $severity_list[$log_entry['severity']],
+    '@timestamp'     => format_date($log_entry['timestamp']),
+    '@type'          => $log_entry['type'],
+    '@ip'            => $log_entry['ip'],
+    '@request_uri'   => $log_entry['request_uri'],
+    '@referer_uri'   => $log_entry['referer'],
+    '@uid'           => $log_entry['uid'],
+    '@name'          => $log_entry['user']->name,
+    '@link'          => strip_tags($log_entry['link']),
+    '@message'       => strip_tags($log_entry['message']),
+  ));
+
+  drupal_mail('emaillog', 'entry', $to, $language, $params);
+}
+
+/**
+ * Prepare a message based on parameters; called from drupal_mail().
+ *
+ * Note that hook_mail(), unlike hook_mail_alter(), is only called on the
+ * $module argument to drupal_mail(), not all modules.
+ *
+ * @param $key
+ *   An identifier of the mail.
+ * @param $message
+ *   An array to be filled in. Elements in this array include:
+ *   - id: An ID to identify the mail sent. Look at module source code
+ *     or drupal_mail() for possible id values.
+ *   - to: The address or addresses the message will be sent to. The formatting
+ *     of this string will be validated with the
+ *     @link http://php.net/manual/filter.filters.validate.php PHP e-mail validation filter. @endlink
+ *   - subject: Subject of the e-mail to be sent. This must not contain any
+ *     newline characters, or the mail may not be sent properly. drupal_mail()
+ *     sets this to an empty string when the hook is invoked.
+ *   - body: An array of lines containing the message to be sent. Drupal will
+ *     format the correct line endings for you. drupal_mail() sets this to an
+ *     empty array when the hook is invoked.
+ *   - from: The address the message will be marked as being from, which is
+ *     set by drupal_mail() to either a custom address or the site-wide
+ *     default email address when the hook is invoked.
+ *   - headers: Associative array containing mail headers, such as From,
+ *     Sender, MIME-Version, Content-Type, etc. drupal_mail() pre-fills
+ *     several headers in this array.
+ * @param $params
+ *   An array of parameters supplied by the caller of drupal_mail().
+ */
+function hook_mail($key, &$message, $params) {
+  $account = $params['account'];
+  $context = $params['context'];
+  $variables = array(
+    '%site_name' => variable_get('site_name', 'Drupal'),
+    '%username' => format_username($account),
+  );
+  if ($context['hook'] == 'taxonomy') {
+    $entity = $params['entity'];
+    $vocabulary = taxonomy_vocabulary_load($entity->vid);
+    $variables += array(
+      '%term_name' => $entity->name,
+      '%term_description' => $entity->description,
+      '%term_id' => $entity->tid,
+      '%vocabulary_name' => $vocabulary->name,
+      '%vocabulary_description' => $vocabulary->description,
+      '%vocabulary_id' => $vocabulary->vid,
+    );
+  }
+
+  // Node-based variable translation is only available if we have a node.
+  if (isset($params['node'])) {
+    $node = $params['node'];
+    $variables += array(
+      '%uid' => $node->uid,
+      '%node_url' => url('node/' . $node->nid, array('absolute' => TRUE)),
+      '%node_type' => node_type_get_name($node),
+      '%title' => $node->title,
+      '%teaser' => $node->teaser,
+      '%body' => $node->body,
+    );
+  }
+  $subject = strtr($context['subject'], $variables);
+  $body = strtr($context['message'], $variables);
+  $message['subject'] .= str_replace(array("\r", "\n"), '', $subject);
+  $message['body'][] = drupal_html_to_text($body);
+}
+
+/**
+ * Add a list of cache tables to be cleared.
+ *
+ * This hook allows your module to add cache table names to the list of cache
+ * tables that will be cleared by the Clear button on the Performance page or
+ * whenever drupal_flush_all_caches is invoked.
+ *
+ * @return
+ *   An array of cache table names.
+ *
+ * @see drupal_flush_all_caches()
+ */
+function hook_flush_caches() {
+  return array('cache_example');
+}
+
+/**
+ * Perform necessary actions after modules are installed.
+ *
+ * This function differs from hook_install() in that it gives all other modules
+ * a chance to perform actions when a module is installed, whereas
+ * hook_install() is only called on the module actually being installed. See
+ * module_enable() for a detailed description of the order in which install and
+ * enable hooks are invoked.
+ *
+ * @param $modules
+ *   An array of the modules that were installed.
+ *
+ * @see module_enable()
+ * @see hook_modules_enabled()
+ * @see hook_install()
+ */
+function hook_modules_installed($modules) {
+  if (in_array('lousy_module', $modules)) {
+    variable_set('lousy_module_conflicting_variable', FALSE);
+  }
+}
+
+/**
+ * Perform necessary actions after modules are enabled.
+ *
+ * This function differs from hook_enable() in that it gives all other modules a
+ * chance to perform actions when modules are enabled, whereas hook_enable() is
+ * only called on the module actually being enabled. See module_enable() for a
+ * detailed description of the order in which install and enable hooks are
+ * invoked.
+ *
+ * @param $modules
+ *   An array of the modules that were enabled.
+ *
+ * @see hook_enable()
+ * @see hook_modules_installed()
+ * @see module_enable()
+ */
+function hook_modules_enabled($modules) {
+  if (in_array('lousy_module', $modules)) {
+    drupal_set_message(t('mymodule is not compatible with lousy_module'), 'error');
+    mymodule_disable_functionality();
+  }
+}
+
+/**
+ * Perform necessary actions after modules are disabled.
+ *
+ * This function differs from hook_disable() in that it gives all other modules
+ * a chance to perform actions when modules are disabled, whereas hook_disable()
+ * is only called on the module actually being disabled.
+ *
+ * @param $modules
+ *   An array of the modules that were disabled.
+ *
+ * @see hook_disable()
+ * @see hook_modules_uninstalled()
+ */
+function hook_modules_disabled($modules) {
+  if (in_array('lousy_module', $modules)) {
+    mymodule_enable_functionality();
+  }
+}
+
+/**
+ * Perform necessary actions after modules are uninstalled.
+ *
+ * This function differs from hook_uninstall() in that it gives all other
+ * modules a chance to perform actions when a module is uninstalled, whereas
+ * hook_uninstall() is only called on the module actually being uninstalled.
+ *
+ * It is recommended that you implement this hook if your module stores
+ * data that may have been set by other modules.
+ *
+ * @param $modules
+ *   An array of the modules that were uninstalled.
+ *
+ * @see hook_uninstall()
+ * @see hook_modules_disabled()
+ */
+function hook_modules_uninstalled($modules) {
+  foreach ($modules as $module) {
+    db_delete('mymodule_table')
+      ->condition('module', $module)
+      ->execute();
+  }
+  mymodule_cache_rebuild();
+}
+
+/**
+ * Registers PHP stream wrapper implementations associated with a module.
+ *
+ * Provide a facility for managing and querying user-defined stream wrappers
+ * in PHP. PHP's internal stream_get_wrappers() doesn't return the class
+ * registered to handle a stream, which we need to be able to find the handler
+ * for class instantiation.
+ *
+ * If a module registers a scheme that is already registered with PHP, it will
+ * be unregistered and replaced with the specified class.
+ *
+ * @return
+ *   A nested array, keyed first by scheme name ("public" for "public://"),
+ *   then keyed by the following values:
+ *   - 'name' A short string to name the wrapper.
+ *   - 'class' A string specifying the PHP class that implements the
+ *     DrupalStreamWrapperInterface interface.
+ *   - 'description' A string with a short description of what the wrapper does.
+ *   - 'type' (Optional) A bitmask of flags indicating what type of streams this
+ *     wrapper will access - local or remote, readable and/or writeable, etc.
+ *     Many shortcut constants are defined in stream_wrappers.inc. Defaults to
+ *     STREAM_WRAPPERS_NORMAL which includes all of these bit flags:
+ *     - STREAM_WRAPPERS_READ
+ *     - STREAM_WRAPPERS_WRITE
+ *     - STREAM_WRAPPERS_VISIBLE
+ *
+ * @see file_get_stream_wrappers()
+ * @see hook_stream_wrappers_alter()
+ * @see system_stream_wrappers()
+ */
+function hook_stream_wrappers() {
+  return array(
+    'public' => array(
+      'name' => t('Public files'),
+      'class' => 'DrupalPublicStreamWrapper',
+      'description' => t('Public local files served by the webserver.'),
+      'type' => STREAM_WRAPPERS_LOCAL_NORMAL,
+    ),
+    'private' => array(
+      'name' => t('Private files'),
+      'class' => 'DrupalPrivateStreamWrapper',
+      'description' => t('Private local files served by Drupal.'),
+      'type' => STREAM_WRAPPERS_LOCAL_NORMAL,
+    ),
+    'temp' => array(
+      'name' => t('Temporary files'),
+      'class' => 'DrupalTempStreamWrapper',
+      'description' => t('Temporary local files for upload and previews.'),
+      'type' => STREAM_WRAPPERS_LOCAL_HIDDEN,
+    ),
+    'cdn' => array(
+      'name' => t('Content delivery network files'),
+      'class' => 'MyModuleCDNStreamWrapper',
+      'description' => t('Files served by a content delivery network.'),
+      // 'type' can be omitted to use the default of STREAM_WRAPPERS_NORMAL
+    ),
+    'youtube' => array(
+      'name' => t('YouTube video'),
+      'class' => 'MyModuleYouTubeStreamWrapper',
+      'description' => t('Video streamed from YouTube.'),
+      // A module implementing YouTube integration may decide to support using
+      // the YouTube API for uploading video, but here, we assume that this
+      // particular module only supports playing YouTube video.
+      'type' => STREAM_WRAPPERS_READ_VISIBLE,
+    ),
+  );
+}
+
+/**
+ * Alters the list of PHP stream wrapper implementations.
+ *
+ * @see file_get_stream_wrappers()
+ * @see hook_stream_wrappers()
+ */
+function hook_stream_wrappers_alter(&$wrappers) {
+  // Change the name of private files to reflect the performance.
+  $wrappers['private']['name'] = t('Slow files');
+}
+
+/**
+ * Load additional information into file objects.
+ *
+ * file_load_multiple() calls this hook to allow modules to load
+ * additional information into each file.
+ *
+ * @param $files
+ *   An array of file objects, indexed by fid.
+ *
+ * @see file_load_multiple()
+ * @see file_load()
+ */
+function hook_file_load($files) {
+  // Add the upload specific data into the file object.
+  $result = db_query('SELECT * FROM {upload} u WHERE u.fid IN (:fids)', array(':fids' => array_keys($files)))->fetchAll(PDO::FETCH_ASSOC);
+  foreach ($result as $record) {
+    foreach ($record as $key => $value) {
+      $files[$record['fid']]->$key = $value;
+    }
+  }
+}
+
+/**
+ * Check that files meet a given criteria.
+ *
+ * This hook lets modules perform additional validation on files. They're able
+ * to report a failure by returning one or more error messages.
+ *
+ * @param $file
+ *   The file object being validated.
+ * @return
+ *   An array of error messages. If there are no problems with the file return
+ *   an empty array.
+ *
+ * @see file_validate()
+ */
+function hook_file_validate($file) {
+  $errors = array();
+
+  if (empty($file->filename)) {
+    $errors[] = t("The file's name is empty. Please give a name to the file.");
+  }
+  if (strlen($file->filename) > 255) {
+    $errors[] = t("The file's name exceeds the 255 characters limit. Please rename the file and try again.");
+  }
+
+  return $errors;
+}
+
+/**
+ * Act on a file being inserted or updated.
+ *
+ * This hook is called when a file has been added to the database. The hook
+ * doesn't distinguish between files created as a result of a copy or those
+ * created by an upload.
+ *
+ * @param $file
+ *   The file that has just been created.
+ *
+ * @see file_save()
+ */
+function hook_file_presave($file) {
+  // Change the file timestamp to an hour prior.
+  $file->timestamp -= 3600;
+}
+
+/**
+ * Respond to a file being added.
+ *
+ * This hook is called after a file has been added to the database. The hook
+ * doesn't distinguish between files created as a result of a copy or those
+ * created by an upload.
+ *
+ * @param $file
+ *   The file that has been added.
+ *
+ * @see file_save()
+ */
+function hook_file_insert($file) {
+  // Add a message to the log, if the file is a jpg
+  $validate = file_validate_extensions($file, 'jpg');
+  if (empty($validate)) {
+    watchdog('file', 'A jpg has been added.');
+  }
+}
+
+/**
+ * Respond to a file being updated.
+ *
+ * This hook is called when file_save() is called on an existing file.
+ *
+ * @param $file
+ *   The file that has just been updated.
+ *
+ * @see file_save()
+ */
+function hook_file_update($file) {
+  $file_user = user_load($file->uid);
+  // Make sure that the file name starts with the owner's user name.
+  if (strpos($file->filename, $file_user->name) !== 0) {
+    $old_filename = $file->filename;
+    $file->filename = $file_user->name . '_' . $file->filename;
+    $file->save();
+
+    watchdog('file', t('%source has been renamed to %destination', array('%source' => $old_filename, '%destination' => $file->filename)));
+  }
+}
+
+/**
+ * Respond to a file that has been copied.
+ *
+ * @param $file
+ *   The newly copied file object.
+ * @param $source
+ *   The original file before the copy.
+ *
+ * @see file_copy()
+ */
+function hook_file_copy($file, $source) {
+  $file_user = user_load($file->uid);
+  // Make sure that the file name starts with the owner's user name.
+  if (strpos($file->filename, $file_user->name) !== 0) {
+    $file->filename = $file_user->name . '_' . $file->filename;
+    $file->save();
+
+    watchdog('file', t('Copied file %source has been renamed to %destination', array('%source' => $source->filename, '%destination' => $file->filename)));
+  }
+}
+
+/**
+ * Respond to a file that has been moved.
+ *
+ * @param $file
+ *   The updated file object after the move.
+ * @param $source
+ *   The original file object before the move.
+ *
+ * @see file_move()
+ */
+function hook_file_move($file, $source) {
+  $file_user = user_load($file->uid);
+  // Make sure that the file name starts with the owner's user name.
+  if (strpos($file->filename, $file_user->name) !== 0) {
+    $file->filename = $file_user->name . '_' . $file->filename;
+    $file->save();
+
+    watchdog('file', t('Moved file %source has been renamed to %destination', array('%source' => $source->filename, '%destination' => $file->filename)));
+  }
+}
+
+/**
+ * Respond to a file being deleted.
+ *
+ * @param $file
+ *   The file that has just been deleted.
+ *
+ * @see file_delete()
+ */
+function hook_file_delete($file) {
+  // Delete all information associated with the file.
+  db_delete('upload')->condition('fid', $file->fid)->execute();
+}
+
+/**
+ * Control access to private file downloads and specify HTTP headers.
+ *
+ * This hook allows modules enforce permissions on file downloads when the
+ * private file download method is selected. Modules can also provide headers
+ * to specify information like the file's name or MIME type.
+ *
+ * @param $uri
+ *   The URI of the file.
+ * @return
+ *   If the user does not have permission to access the file, return -1. If the
+ *   user has permission, return an array with the appropriate headers. If the
+ *   file is not controlled by the current module, the return value should be
+ *   NULL.
+ *
+ * @see file_download()
+ */
+function hook_file_download($uri) {
+  // Check if the file is controlled by the current module.
+  if (!file_prepare_directory($uri)) {
+    $uri = FALSE;
+  }
+  if (strpos(file_uri_target($uri), variable_get('user_picture_path', 'pictures') . '/picture-') === 0) {
+    if (!user_access('access user profiles')) {
+      // Access to the file is denied.
+      return -1;
+    }
+    else {
+      $info = image_get_info($uri);
+      return array('Content-Type' => $info['mime_type']);
+    }
+  }
+}
+
+/**
+ * Alter the URL to a file.
+ *
+ * This hook is called from file_create_url(), and  is called fairly
+ * frequently (10+ times per page), depending on how many files there are in a
+ * given page.
+ * If CSS and JS aggregation are disabled, this can become very frequently
+ * (50+ times per page) so performance is critical.
+ *
+ * This function should alter the URI, if it wants to rewrite the file URL.
+ *
+ * @param $uri
+ *   The URI to a file for which we need an external URL, or the path to a
+ *   shipped file.
+ */
+function hook_file_url_alter(&$uri) {
+  global $user;
+
+  // User 1 will always see the local file in this example.
+  if ($user->uid == 1) {
+    return;
+  }
+
+  $cdn1 = 'http://cdn1.example.com';
+  $cdn2 = 'http://cdn2.example.com';
+  $cdn_extensions = array('css', 'js', 'gif', 'jpg', 'jpeg', 'png');
+
+  // Most CDNs don't support private file transfers without a lot of hassle,
+  // so don't support this in the common case.
+  $schemes = array('public');
+
+  $scheme = file_uri_scheme($uri);
+
+  // Only serve shipped files and public created files from the CDN.
+  if (!$scheme || in_array($scheme, $schemes)) {
+    // Shipped files.
+    if (!$scheme) {
+      $path = $uri;
+    }
+    // Public created files.
+    else {
+      $wrapper = file_stream_wrapper_get_instance_by_scheme($scheme);
+      $path = $wrapper->getDirectoryPath() . '/' . file_uri_target($uri);
+    }
+
+    // Clean up Windows paths.
+    $path = str_replace('\\', '/', $path);
+
+    // Serve files with one of the CDN extensions from CDN 1, all others from
+    // CDN 2.
+    $pathinfo = pathinfo($path);
+    if (isset($pathinfo['extension']) && in_array($pathinfo['extension'], $cdn_extensions)) {
+      $uri = $cdn1 . '/' . $path;
+    }
+    else {
+      $uri = $cdn2 . '/' . $path;
+    }
+  }
+}
+
+/**
+ * Check installation requirements and do status reporting.
+ *
+ * This hook has three closely related uses, determined by the $phase argument:
+ * - Checking installation requirements ($phase == 'install').
+ * - Checking update requirements ($phase == 'update').
+ * - Status reporting ($phase == 'runtime').
+ *
+ * Note that this hook, like all others dealing with installation and updates,
+ * must reside in a module_name.install file, or it will not properly abort
+ * the installation of the module if a critical requirement is missing.
+ *
+ * During the 'install' phase, modules can for example assert that
+ * library or server versions are available or sufficient.
+ * Note that the installation of a module can happen during installation of
+ * Drupal itself (by install.php) with an installation profile or later by hand.
+ * As a consequence, install-time requirements must be checked without access
+ * to the full Drupal API, because it is not available during install.php.
+ * For localization you should for example use $t = get_t() to
+ * retrieve the appropriate localization function name (t() or st()).
+ * If a requirement has a severity of REQUIREMENT_ERROR, install.php will abort
+ * or at least the module will not install.
+ * Other severity levels have no effect on the installation.
+ * Module dependencies do not belong to these installation requirements,
+ * but should be defined in the module's .info file.
+ *
+ * The 'runtime' phase is not limited to pure installation requirements
+ * but can also be used for more general status information like maintenance
+ * tasks and security issues.
+ * The returned 'requirements' will be listed on the status report in the
+ * administration section, with indication of the severity level.
+ * Moreover, any requirement with a severity of REQUIREMENT_ERROR severity will
+ * result in a notice on the administration configuration page.
+ *
+ * @param $phase
+ *   The phase in which requirements are checked:
+ *   - install: The module is being installed.
+ *   - update: The module is enabled and update.php is run.
+ *   - runtime: The runtime requirements are being checked and shown on the
+ *     status report page.
+ *
+ * @return
+ *   An associative array where the keys are arbitrary but must be unique (it
+ *   is suggested to use the module short name as a prefix) and the values are
+ *   themselves associative arrays with the following elements:
+ *   - title: The name of the requirement.
+ *   - value: The current value (e.g., version, time, level, etc). During
+ *     install phase, this should only be used for version numbers, do not set
+ *     it if not applicable.
+ *   - description: The description of the requirement/status.
+ *   - severity: The requirement's result/severity level, one of:
+ *     - REQUIREMENT_INFO: For info only.
+ *     - REQUIREMENT_OK: The requirement is satisfied.
+ *     - REQUIREMENT_WARNING: The requirement failed with a warning.
+ *     - REQUIREMENT_ERROR: The requirement failed with an error.
+ */
+function hook_requirements($phase) {
+  $requirements = array();
+  // Ensure translations don't break during installation.
+  $t = get_t();
+
+  // Report Drupal version
+  if ($phase == 'runtime') {
+    $requirements['drupal'] = array(
+      'title' => $t('Drupal'),
+      'value' => VERSION,
+      'severity' => REQUIREMENT_INFO
+    );
+  }
+
+  // Test PHP version
+  $requirements['php'] = array(
+    'title' => $t('PHP'),
+    'value' => ($phase == 'runtime') ? l(phpversion(), 'admin/reports/status/php') : phpversion(),
+  );
+  if (version_compare(phpversion(), DRUPAL_MINIMUM_PHP) < 0) {
+    $requirements['php']['description'] = $t('Your PHP installation is too old. Drupal requires at least PHP %version.', array('%version' => DRUPAL_MINIMUM_PHP));
+    $requirements['php']['severity'] = REQUIREMENT_ERROR;
+  }
+
+  // Report cron status
+  if ($phase == 'runtime') {
+    $cron_last = variable_get('cron_last');
+
+    if (is_numeric($cron_last)) {
+      $requirements['cron']['value'] = $t('Last run !time ago', array('!time' => format_interval(REQUEST_TIME - $cron_last)));
+    }
+    else {
+      $requirements['cron'] = array(
+        'description' => $t('Cron has not run. It appears cron jobs have not been setup on your system. Check the help pages for <a href="@url">configuring cron jobs</a>.', array('@url' => 'http://drupal.org/cron')),
+        'severity' => REQUIREMENT_ERROR,
+        'value' => $t('Never run'),
+      );
+    }
+
+    $requirements['cron']['description'] .= ' ' . $t('You can <a href="@cron">run cron manually</a>.', array('@cron' => url('admin/reports/status/run-cron')));
+
+    $requirements['cron']['title'] = $t('Cron maintenance tasks');
+  }
+
+  return $requirements;
+}
+
+/**
+ * Define the current version of the database schema.
+ *
+ * A Drupal schema definition is an array structure representing one or
+ * more tables and their related keys and indexes. A schema is defined by
+ * hook_schema() which must live in your module's .install file.
+ *
+ * This hook is called at install and uninstall time, and in the latter
+ * case, it cannot rely on the .module file being loaded or hooks being known.
+ * If the .module file is needed, it may be loaded with drupal_load().
+ *
+ * The tables declared by this hook will be automatically created when
+ * the module is first enabled, and removed when the module is uninstalled.
+ * This happens before hook_install() is invoked, and after hook_uninstall()
+ * is invoked, respectively.
+ *
+ * By declaring the tables used by your module via an implementation of
+ * hook_schema(), these tables will be available on all supported database
+ * engines. You don't have to deal with the different SQL dialects for table
+ * creation and alteration of the supported database engines.
+ *
+ * See the Schema API Handbook at http://drupal.org/node/146843 for
+ * details on schema definition structures.
+ *
+ * @return
+ *   A schema definition structure array. For each element of the
+ *   array, the key is a table name and the value is a table structure
+ *   definition.
+ *
+ * @ingroup schemaapi
+ */
+function hook_schema() {
+  $schema['node'] = array(
+    // example (partial) specification for table "node"
+    'description' => 'The base table for nodes.',
+    'fields' => array(
+      'nid' => array(
+        'description' => 'The primary identifier for a node.',
+        'type' => 'serial',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+      ),
+      'vid' => array(
+        'description' => 'The current {node_revision}.vid version identifier.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'type' => array(
+        'description' => 'The {node_type} of this node.',
+        'type' => 'varchar',
+        'length' => 32,
+        'not null' => TRUE,
+        'default' => '',
+      ),
+      'title' => array(
+        'description' => 'The title of this node, always treated as non-markup plain text.',
+        'type' => 'varchar',
+        'length' => 255,
+        'not null' => TRUE,
+        'default' => '',
+      ),
+    ),
+    'indexes' => array(
+      'node_changed'        => array('changed'),
+      'node_created'        => array('created'),
+    ),
+    'unique keys' => array(
+      'nid_vid' => array('nid', 'vid'),
+      'vid'     => array('vid'),
+    ),
+    'foreign keys' => array(
+      'node_revision' => array(
+        'table' => 'node_revision',
+        'columns' => array('vid' => 'vid'),
+      ),
+      'node_author' => array(
+        'table' => 'users',
+        'columns' => array('uid' => 'uid'),
+      ),
+    ),
+    'primary key' => array('nid'),
+  );
+  return $schema;
+}
+
+/**
+ * Perform alterations to existing database schemas.
+ *
+ * When a module modifies the database structure of another module (by
+ * changing, adding or removing fields, keys or indexes), it should
+ * implement hook_schema_alter() to update the default $schema to take its
+ * changes into account.
+ *
+ * See hook_schema() for details on the schema definition structure.
+ *
+ * @param $schema
+ *   Nested array describing the schemas for all modules.
+ *
+ * @ingroup schemaapi
+ */
+function hook_schema_alter(&$schema) {
+  // Add field to existing schema.
+  $schema['users']['fields']['timezone_id'] = array(
+    'type' => 'int',
+    'not null' => TRUE,
+    'default' => 0,
+    'description' => 'Per-user timezone configuration.',
+  );
+}
+
+/**
+ * Perform alterations to a structured query.
+ *
+ * Structured (aka dynamic) queries that have tags associated may be altered by any module
+ * before the query is executed.
+ *
+ * @param $query
+ *   A Query object describing the composite parts of a SQL query.
+ *
+ * @see hook_query_TAG_alter()
+ * @see node_query_node_access_alter()
+ * @see QueryAlterableInterface
+ * @see SelectQueryInterface
+ */
+function hook_query_alter(QueryAlterableInterface $query) {
+  if ($query->hasTag('micro_limit')) {
+    $query->range(0, 2);
+  }
+}
+
+/**
+ * Perform alterations to a structured query for a given tag.
+ *
+ * @param $query
+ *   An Query object describing the composite parts of a SQL query.
+ *
+ * @see hook_query_alter()
+ * @see node_query_node_access_alter()
+ * @see QueryAlterableInterface
+ * @see SelectQueryInterface
+ */
+function hook_query_TAG_alter(QueryAlterableInterface $query) {
+  // Skip the extra expensive alterations if site has no node access control modules.
+  if (!node_access_view_all_nodes()) {
+    // Prevent duplicates records.
+    $query->distinct();
+    // The recognized operations are 'view', 'update', 'delete'.
+    if (!$op = $query->getMetaData('op')) {
+      $op = 'view';
+    }
+    // Skip the extra joins and conditions for node admins.
+    if (!user_access('bypass node access')) {
+      // The node_access table has the access grants for any given node.
+      $access_alias = $query->join('node_access', 'na', '%alias.nid = n.nid');
+      $or = db_or();
+      // If any grant exists for the specified user, then user has access to the node for the specified operation.
+      foreach (node_access_grants($op, $query->getMetaData('account')) as $realm => $gids) {
+        foreach ($gids as $gid) {
+          $or->condition(db_and()
+            ->condition($access_alias . '.gid', $gid)
+            ->condition($access_alias . '.realm', $realm)
+          );
+        }
+      }
+
+      if (count($or->conditions())) {
+        $query->condition($or);
+      }
+
+      $query->condition($access_alias . 'grant_' . $op, 1, '>=');
+    }
+  }
+}
+
+/**
+ * Perform setup tasks when the module is installed.
+ *
+ * If the module implements hook_schema(), the database tables will
+ * be created before this hook is fired.
+ *
+ * Implementations of this hook are by convention declared in the module's
+ * .install file. The implementation can rely on the .module file being loaded.
+ * The hook will only be called the first time a module is enabled or after it
+ * is re-enabled after being uninstalled. The module's schema version will be
+ * set to the module's greatest numbered update hook. Because of this, any time
+ * a hook_update_N() is added to the module, this function needs to be updated
+ * to reflect the current version of the database schema.
+ *
+ * See the @link http://drupal.org/node/146843 Schema API documentation @endlink
+ * for details on hook_schema and how database tables are defined.
+ *
+ * Note that since this function is called from a full bootstrap, all functions
+ * (including those in modules enabled by the current page request) are
+ * available when this hook is called. Use cases could be displaying a user
+ * message, or calling a module function necessary for initial setup, etc.
+ *
+ * Please be sure that anything added or modified in this function that can
+ * be removed during uninstall should be removed with hook_uninstall().
+ *
+ * @see hook_schema()
+ * @see module_enable()
+ * @see hook_enable()
+ * @see hook_disable()
+ * @see hook_uninstall()
+ * @see hook_modules_installed()
+ */
+function hook_install() {
+  // Populate the default {node_access} record.
+  db_insert('node_access')
+    ->fields(array(
+      'nid' => 0,
+      'gid' => 0,
+      'realm' => 'all',
+      'grant_view' => 1,
+      'grant_update' => 0,
+      'grant_delete' => 0,
+    ))
+    ->execute();
+}
+
+/**
+ * Perform a single update.
+ *
+ * For each change that requires one or more actions to be performed when
+ * updating a site, add a new hook_update_N(), which will be called by
+ * update.php. The documentation block preceding this function is stripped of
+ * newlines and used as the description for the update on the pending updates
+ * task list. Schema updates should adhere to the
+ * @link http://drupal.org/node/150215 Schema API. @endlink
+ *
+ * Implementations of hook_update_N() are named (module name)_update_(number).
+ * The numbers are composed of three parts:
+ * - 1 digit for Drupal core compatibility.
+ * - 1 digit for your module's major release version (e.g., is this the 7.x-1.*
+ *   (1) or 7.x-2.* (2) series of your module?). This digit should be 0 for
+ *   initial porting of your module to a new Drupal core API.
+ * - 2 digits for sequential counting, starting with 00.
+ *
+ * Examples:
+ * - mymodule_update_7000(): This is the required update for mymodule to run
+ *   with Drupal core API 7.x when upgrading from Drupal core API 6.x.
+ * - mymodule_update_7100(): This is the first update to get the database ready
+ *   to run mymodule 7.x-1.*.
+ * - mymodule_update_7200(): This is the first update to get the database ready
+ *   to run mymodule 7.x-2.*. Users can directly update from 6.x-2.* to 7.x-2.*
+ *   and they get all 70xx and 72xx updates, but not 71xx updates, because
+ *   those reside in the 7.x-1.x branch only.
+ *
+ * A good rule of thumb is to remove updates older than two major releases of
+ * Drupal. See hook_update_last_removed() to notify Drupal about the removals.
+ * For further information about releases and release numbers see:
+ * @link http://drupal.org/node/711070 Maintaining a drupal.org project with Git @endlink
+ *
+ * Never renumber update functions.
+ *
+ * Implementations of this hook should be placed in a mymodule.install file in
+ * the same directory as mymodule.module. Drupal core's updates are implemented
+ * using the system module as a name and stored in database/updates.inc.
+ *
+ * Not all module functions are available from within a hook_update_N() function.
+ * In order to call a function from your mymodule.module or an include file,
+ * you need to explicitly load that file first.
+ *
+ * During database updates the schema of any module could be out of date. For
+ * this reason, caution is needed when using any API function within an update
+ * function - particularly CRUD functions, functions that depend on the schema
+ * (for example by using drupal_write_record()), and any functions that invoke
+ * hooks. See @link update_api Update versions of API functions @endlink for
+ * details.
+ *
+ * If your update task is potentially time-consuming, you'll need to implement a
+ * multipass update to avoid PHP timeouts. Multipass updates use the $sandbox
+ * parameter provided by the batch API (normally, $context['sandbox']) to store
+ * information between successive calls, and the $sandbox['#finished'] value
+ * to provide feedback regarding completion level.
+ *
+ * See the batch operations page for more information on how to use the
+ * @link http://drupal.org/node/180528 Batch API. @endlink
+ *
+ * @param $sandbox
+ *   Stores information for multipass updates. See above for more information.
+ *
+ * @throws DrupalUpdateException, PDOException
+ *   In case of error, update hooks should throw an instance of DrupalUpdateException
+ *   with a meaningful message for the user. If a database query fails for whatever
+ *   reason, it will throw a PDOException.
+ *
+ * @return
+ *   Optionally, update hooks may return a translated string that will be
+ *   displayed to the user after the update has completed. If no message is
+ *   returned, no message will be presented to the user.
+ *
+ * @see batch
+ * @see schemaapi
+ * @see update_api
+ * @see hook_update_last_removed()
+ * @see update_get_update_list()
+ */
+function hook_update_N(&$sandbox) {
+  // For non-multipass updates, the signature can simply be;
+  // function hook_update_N() {
+
+  // For most updates, the following is sufficient.
+  db_add_field('mytable1', 'newcol', array('type' => 'int', 'not null' => TRUE, 'description' => 'My new integer column.'));
+
+  // However, for more complex operations that may take a long time,
+  // you may hook into Batch API as in the following example.
+
+  // Update 3 users at a time to have an exclamation point after their names.
+  // (They're really happy that we can do batch API in this hook!)
+  if (!isset($sandbox['progress'])) {
+    $sandbox['progress'] = 0;
+    $sandbox['current_uid'] = 0;
+    // We'll -1 to disregard the uid 0...
+    $sandbox['max'] = db_query('SELECT COUNT(DISTINCT uid) FROM {users}')->fetchField() - 1;
+  }
+
+  $users = db_select('users', 'u')
+    ->fields('u', array('uid', 'name'))
+    ->condition('uid', $sandbox['current_uid'], '>')
+    ->range(0, 3)
+    ->orderBy('uid', 'ASC')
+    ->execute();
+
+  foreach ($users as $user) {
+    $user->name .= '!';
+    db_update('users')
+      ->fields(array('name' => $user->name))
+      ->condition('uid', $user->uid)
+      ->execute();
+
+    $sandbox['progress']++;
+    $sandbox['current_uid'] = $user->uid;
+  }
+
+  $sandbox['#finished'] = empty($sandbox['max']) ? 1 : ($sandbox['progress'] / $sandbox['max']);
+
+  // To display a message to the user when the update is completed, return it.
+  // If you do not want to display a completion message, simply return nothing.
+  return t('The update did what it was supposed to do.');
+
+  // In case of an error, simply throw an exception with an error message.
+  throw new DrupalUpdateException('Something went wrong; here is what you should do.');
+}
+
+/**
+ * Return an array of information about module update dependencies.
+ *
+ * This can be used to indicate update functions from other modules that your
+ * module's update functions depend on, or vice versa. It is used by the update
+ * system to determine the appropriate order in which updates should be run, as
+ * well as to search for missing dependencies.
+ *
+ * Implementations of this hook should be placed in a mymodule.install file in
+ * the same directory as mymodule.module.
+ *
+ * @return
+ *   A multidimensional array containing information about the module update
+ *   dependencies. The first two levels of keys represent the module and update
+ *   number (respectively) for which information is being returned, and the
+ *   value is an array of information about that update's dependencies. Within
+ *   this array, each key represents a module, and each value represents the
+ *   number of an update function within that module. In the event that your
+ *   update function depends on more than one update from a particular module,
+ *   you should always list the highest numbered one here (since updates within
+ *   a given module always run in numerical order).
+ *
+ * @see update_resolve_dependencies()
+ * @see hook_update_N()
+ */
+function hook_update_dependencies() {
+  // Indicate that the mymodule_update_7000() function provided by this module
+  // must run after the another_module_update_7002() function provided by the
+  // 'another_module' module.
+  $dependencies['mymodule'][7000] = array(
+    'another_module' => 7002,
+  );
+  // Indicate that the mymodule_update_7001() function provided by this module
+  // must run before the yet_another_module_update_7004() function provided by
+  // the 'yet_another_module' module. (Note that declaring dependencies in this
+  // direction should be done only in rare situations, since it can lead to the
+  // following problem: If a site has already run the yet_another_module
+  // module's database updates before it updates its codebase to pick up the
+  // newest mymodule code, then the dependency declared here will be ignored.)
+  $dependencies['yet_another_module'][7004] = array(
+    'mymodule' => 7001,
+  );
+  return $dependencies;
+}
+
+/**
+ * Return a number which is no longer available as hook_update_N().
+ *
+ * If you remove some update functions from your mymodule.install file, you
+ * should notify Drupal of those missing functions. This way, Drupal can
+ * ensure that no update is accidentally skipped.
+ *
+ * Implementations of this hook should be placed in a mymodule.install file in
+ * the same directory as mymodule.module.
+ *
+ * @return
+ *   An integer, corresponding to hook_update_N() which has been removed from
+ *   mymodule.install.
+ *
+ * @see hook_update_N()
+ */
+function hook_update_last_removed() {
+  // We've removed the 5.x-1.x version of mymodule, including database updates.
+  // The next update function is mymodule_update_5200().
+  return 5103;
+}
+
+/**
+ * Remove any information that the module sets.
+ *
+ * The information that the module should remove includes:
+ * - variables that the module has set using variable_set() or system_settings_form()
+ * - modifications to existing tables
+ *
+ * The module should not remove its entry from the {system} table. Database
+ * tables defined by hook_schema() will be removed automatically.
+ *
+ * The uninstall hook must be implemented in the module's .install file. It
+ * will fire when the module gets uninstalled but before the module's database
+ * tables are removed, allowing your module to query its own tables during
+ * this routine.
+ *
+ * When hook_uninstall() is called, your module will already be disabled, so
+ * its .module file will not be automatically included. If you need to call API
+ * functions from your .module file in this hook, use drupal_load() to make
+ * them available. (Keep this usage to a minimum, though, especially when
+ * calling API functions that invoke hooks, or API functions from modules
+ * listed as dependencies, since these may not be available or work as expected
+ * when the module is disabled.)
+ *
+ * @see hook_install()
+ * @see hook_schema()
+ * @see hook_disable()
+ * @see hook_modules_uninstalled()
+ */
+function hook_uninstall() {
+  variable_del('upload_file_types');
+}
+
+/**
+ * Perform necessary actions after module is enabled.
+ *
+ * The hook is called every time the module is enabled. It should be
+ * implemented in the module's .install file. The implementation can
+ * rely on the .module file being loaded.
+ *
+ * @see module_enable()
+ * @see hook_install()
+ * @see hook_modules_enabled()
+ */
+function hook_enable() {
+  mymodule_cache_rebuild();
+}
+
+/**
+ * Perform necessary actions before module is disabled.
+ *
+ * The hook is called every time the module is disabled. It should be
+ * implemented in the module's .install file. The implementation can rely
+ * on the .module file being loaded.
+ *
+ * @see hook_uninstall()
+ * @see hook_modules_disabled()
+ */
+function hook_disable() {
+  mymodule_cache_rebuild();
+}
+
+/**
+ * Perform necessary alterations to the list of files parsed by the registry.
+ *
+ * Modules can manually modify the list of files before the registry parses
+ * them. The $modules array provides the .info file information, which includes
+ * the list of files registered to each module. Any files in the list can then
+ * be added to the list of files that the registry will parse, or modify
+ * attributes of a file.
+ *
+ * A necessary alteration made by the core SimpleTest module is to force .test
+ * files provided by disabled modules into the list of files parsed by the
+ * registry.
+ *
+ * @param $files
+ *   List of files to be parsed by the registry. The list will contain
+ *   files found in each enabled module's info file and the core includes
+ *   directory. The array is keyed by the file path and contains an array of
+ *   the related module's name and weight as used internally by
+ *   _registry_update() and related functions.
+ *
+ *   For example:
+ *   @code
+ *     $files["modules/system/system.module"] = array(
+ *       'module' => 'system',
+ *       'weight' => 0,
+ *     );
+ *   @endcode
+ * @param $modules
+ *   An array containing all module information stored in the {system} table.
+ *   Each element of the array also contains the module's .info file
+ *   information in the property 'info'. An additional 'dir' property has been
+ *   added to the module information which provides the path to the directory
+ *   in which the module resides. The example shows how to take advantage of
+ *   both properties.
+ *
+ * @see _registry_update()
+ * @see simpletest_test_get_all()
+ */
+function hook_registry_files_alter(&$files, $modules) {
+  foreach ($modules as $module) {
+    // Only add test files for disabled modules, as enabled modules should
+    // already include any test files they provide.
+    if (!$module->status) {
+      $dir = $module->dir;
+      foreach ($module->info['files'] as $file) {
+        if (substr($file, -5) == '.test') {
+          $files["$dir/$file"] = array('module' => $module->name, 'weight' => $module->weight);
+        }
+      }
+    }
+  }
+}
+
+/**
+ * Return an array of tasks to be performed by an installation profile.
+ *
+ * Any tasks you define here will be run, in order, after the installer has
+ * finished the site configuration step but before it has moved on to the
+ * final import of languages and the end of the installation. You can have any
+ * number of custom tasks to perform during this phase.
+ *
+ * Each task you define here corresponds to a callback function which you must
+ * separately define and which is called when your task is run. This function
+ * will receive the global installation state variable, $install_state, as
+ * input, and has the opportunity to access or modify any of its settings. See
+ * the install_state_defaults() function in the installer for the list of
+ * $install_state settings used by Drupal core.
+ *
+ * At the end of your task function, you can indicate that you want the
+ * installer to pause and display a page to the user by returning any themed
+ * output that should be displayed on that page (but see below for tasks that
+ * use the form API or batch API; the return values of these task functions are
+ * handled differently). You should also use drupal_set_title() within the task
+ * callback function to set a custom page title. For some tasks, however, you
+ * may want to simply do some processing and pass control to the next task
+ * without ending the page request; to indicate this, simply do not send back
+ * a return value from your task function at all. This can be used, for
+ * example, by installation profiles that need to configure certain site
+ * settings in the database without obtaining any input from the user.
+ *
+ * The task function is treated specially if it defines a form or requires
+ * batch processing; in that case, you should return either the form API
+ * definition or batch API array, as appropriate. See below for more
+ * information on the 'type' key that you must define in the task definition
+ * to inform the installer that your task falls into one of those two
+ * categories. It is important to use these APIs directly, since the installer
+ * may be run non-interactively (for example, via a command line script), all
+ * in one page request; in that case, the installer will automatically take
+ * care of submitting forms and processing batches correctly for both types of
+ * installations. You can inspect the $install_state['interactive'] boolean to
+ * see whether or not the current installation is interactive, if you need
+ * access to this information.
+ *
+ * Remember that a user installing Drupal interactively will be able to reload
+ * an installation page multiple times, so you should use variable_set() and
+ * variable_get() if you are collecting any data that you need to store and
+ * inspect later. It is important to remove any temporary variables using
+ * variable_del() before your last task has completed and control is handed
+ * back to the installer.
+ *
+ * @param array $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return array
+ *   A keyed array of tasks the profile will perform during the final stage of
+ *   the installation. Each key represents the name of a function (usually a
+ *   function defined by this profile, although that is not strictly required)
+ *   that is called when that task is run. The values are associative arrays
+ *   containing the following key-value pairs (all of which are optional):
+ *   - display_name: The human-readable name of the task. This will be
+ *     displayed to the user while the installer is running, along with a list
+ *     of other tasks that are being run. Leave this unset to prevent the task
+ *     from appearing in the list.
+ *   - display: This is a boolean which can be used to provide finer-grained
+ *     control over whether or not the task will display. This is mostly useful
+ *     for tasks that are intended to display only under certain conditions;
+ *     for these tasks, you can set 'display_name' to the name that you want to
+ *     display, but then use this boolean to hide the task only when certain
+ *     conditions apply.
+ *   - type: A string representing the type of task. This parameter has three
+ *     possible values:
+ *     - normal: (default) This indicates that the task will be treated as a
+ *       regular callback function, which does its processing and optionally
+ *       returns HTML output.
+ *     - batch: This indicates that the task function will return a batch API
+ *       definition suitable for batch_set(). The installer will then take care
+ *       of automatically running the task via batch processing.
+ *     - form: This indicates that the task function will return a standard
+ *       form API definition (and separately define validation and submit
+ *       handlers, as appropriate). The installer will then take care of
+ *       automatically directing the user through the form submission process.
+ *   - run: A constant representing the manner in which the task will be run.
+ *     This parameter has three possible values:
+ *     - INSTALL_TASK_RUN_IF_NOT_COMPLETED: (default) This indicates that the
+ *       task will run once during the installation of the profile.
+ *     - INSTALL_TASK_SKIP: This indicates that the task will not run during
+ *       the current installation page request. It can be used to skip running
+ *       an installation task when certain conditions are met, even though the
+ *       task may still show on the list of installation tasks presented to the
+ *       user.
+ *     - INSTALL_TASK_RUN_IF_REACHED: This indicates that the task will run on
+ *       each installation page request that reaches it. This is rarely
+ *       necessary for an installation profile to use; it is primarily used by
+ *       the Drupal installer for bootstrap-related tasks.
+ *   - function: Normally this does not need to be set, but it can be used to
+ *     force the installer to call a different function when the task is run
+ *     (rather than the function whose name is given by the array key). This
+ *     could be used, for example, to allow the same function to be called by
+ *     two different tasks.
+ *
+ * @see install_state_defaults()
+ * @see batch_set()
+ */
+function hook_install_tasks(&$install_state) {
+  // Here, we define a variable to allow tasks to indicate that a particular,
+  // processor-intensive batch process needs to be triggered later on in the
+  // installation.
+  $myprofile_needs_batch_processing = variable_get('myprofile_needs_batch_processing', FALSE);
+  $tasks = array(
+    // This is an example of a task that defines a form which the user who is
+    // installing the site will be asked to fill out. To implement this task,
+    // your profile would define a function named myprofile_data_import_form()
+    // as a normal form API callback function, with associated validation and
+    // submit handlers. In the submit handler, in addition to saving whatever
+    // other data you have collected from the user, you might also call
+    // variable_set('myprofile_needs_batch_processing', TRUE) if the user has
+    // entered data which requires that batch processing will need to occur
+    // later on.
+    'myprofile_data_import_form' => array(
+      'display_name' => st('Data import options'),
+      'type' => 'form',
+    ),
+    // Similarly, to implement this task, your profile would define a function
+    // named myprofile_settings_form() with associated validation and submit
+    // handlers. This form might be used to collect and save additional
+    // information from the user that your profile needs. There are no extra
+    // steps required for your profile to act as an "installation wizard"; you
+    // can simply define as many tasks of type 'form' as you wish to execute,
+    // and the forms will be presented to the user, one after another.
+    'myprofile_settings_form' => array(
+      'display_name' => st('Additional options'),
+      'type' => 'form',
+    ),
+    // This is an example of a task that performs batch operations. To
+    // implement this task, your profile would define a function named
+    // myprofile_batch_processing() which returns a batch API array definition
+    // that the installer will use to execute your batch operations. Due to the
+    // 'myprofile_needs_batch_processing' variable used here, this task will be
+    // hidden and skipped unless your profile set it to TRUE in one of the
+    // previous tasks.
+    'myprofile_batch_processing' => array(
+      'display_name' => st('Import additional data'),
+      'display' => $myprofile_needs_batch_processing,
+      'type' => 'batch',
+      'run' => $myprofile_needs_batch_processing ? INSTALL_TASK_RUN_IF_NOT_COMPLETED : INSTALL_TASK_SKIP,
+    ),
+    // This is an example of a task that will not be displayed in the list that
+    // the user sees. To implement this task, your profile would define a
+    // function named myprofile_final_site_setup(), in which additional,
+    // automated site setup operations would be performed. Since this is the
+    // last task defined by your profile, you should also use this function to
+    // call variable_del('myprofile_needs_batch_processing') and clean up the
+    // variable that was used above. If you want the user to pass to the final
+    // Drupal installation tasks uninterrupted, return no output from this
+    // function. Otherwise, return themed output that the user will see (for
+    // example, a confirmation page explaining that your profile's tasks are
+    // complete, with a link to reload the current page and therefore pass on
+    // to the final Drupal installation tasks when the user is ready to do so).
+    'myprofile_final_site_setup' => array(
+    ),
+  );
+  return $tasks;
+}
+
+/**
+ * Change the page the user is sent to by drupal_goto().
+ *
+ * @param $path
+ *   A Drupal path or a full URL.
+ * @param $options
+ *   An associative array of additional URL options to pass to url().
+ * @param $http_response_code
+ *   The HTTP status code to use for the redirection. See drupal_goto() for more
+ *   information.
+ */
+function hook_drupal_goto_alter(&$path, &$options, &$http_response_code) {
+  // A good addition to misery module.
+  $http_response_code = 500;
+}
+
+/**
+ * Alter XHTML HEAD tags before they are rendered by drupal_get_html_head().
+ *
+ * Elements available to be altered are only those added using
+ * drupal_add_html_head_link() or drupal_add_html_head(). CSS and JS files
+ * are handled using drupal_add_css() and drupal_add_js(), so the head links
+ * for those files will not appear in the $head_elements array.
+ *
+ * @param $head_elements
+ *   An array of renderable elements. Generally the values of the #attributes
+ *   array will be the most likely target for changes.
+ */
+function hook_html_head_alter(&$head_elements) {
+  foreach ($head_elements as $key => $element) {
+    if (isset($element['#attributes']['rel']) && $element['#attributes']['rel'] == 'canonical') {
+      // I want a custom canonical URL.
+      $head_elements[$key]['#attributes']['href'] = mymodule_canonical_url();
+    }
+  }
+}
+
+/**
+ * Alter the full list of installation tasks.
+ *
+ * @param $tasks
+ *   An array of all available installation tasks, including those provided by
+ *   Drupal core. You can modify this array to change or replace any part of
+ *   the Drupal installation process that occurs after the installation profile
+ *   is selected.
+ * @param $install_state
+ *   An array of information about the current installation state.
+ */
+function hook_install_tasks_alter(&$tasks, $install_state) {
+  // Replace the "Choose language" installation task provided by Drupal core
+  // with a custom callback function defined by this installation profile.
+  $tasks['install_select_locale']['function'] = 'myprofile_locale_selection';
+}
+
+/**
+ * Alter MIME type mappings used to determine MIME type from a file extension.
+ *
+ * This hook is run when file_mimetype_mapping() is called. It is used to
+ * allow modules to add to or modify the default mapping from
+ * file_default_mimetype_mapping().
+ *
+ * @param $mapping
+ *   An array of mimetypes correlated to the extensions that relate to them.
+ *   The array has 'mimetypes' and 'extensions' elements, each of which is an
+ *   array.
+ *
+ * @see file_default_mimetype_mapping()
+ */
+function hook_file_mimetype_mapping_alter(&$mapping) {
+  // Add new MIME type 'drupal/info'.
+  $mapping['mimetypes']['example_info'] = 'drupal/info';
+  // Add new extension '.info' and map it to the 'drupal/info' MIME type.
+  $mapping['extensions']['info'] = 'example_info';
+  // Override existing extension mapping for '.ogg' files.
+  $mapping['extensions']['ogg'] = 189;
+}
+
+/**
+ * Declares information about actions.
+ *
+ * Any module can define actions, and then call actions_do() to make those
+ * actions happen in response to events. The trigger module provides a user
+ * interface for associating actions with module-defined triggers, and it makes
+ * sure the core triggers fire off actions when their events happen.
+ *
+ * An action consists of two or three parts:
+ * - an action definition (returned by this hook)
+ * - a function which performs the action (which by convention is named
+ *   MODULE_description-of-function_action)
+ * - an optional form definition function that defines a configuration form
+ *   (which has the name of the action function with '_form' appended to it.)
+ *
+ * The action function takes two to four arguments, which come from the input
+ * arguments to actions_do().
+ *
+ * @return
+ *   An associative array of action descriptions. The keys of the array
+ *   are the names of the action functions, and each corresponding value
+ *   is an associative array with the following key-value pairs:
+ *   - 'type': The type of object this action acts upon. Core actions have types
+ *     'node', 'user', 'comment', and 'system'.
+ *   - 'label': The human-readable name of the action, which should be passed
+ *     through the t() function for translation.
+ *   - 'configurable': If FALSE, then the action doesn't require any extra
+ *     configuration. If TRUE, then your module must define a form function with
+ *     the same name as the action function with '_form' appended (e.g., the
+ *     form for 'node_assign_owner_action' is 'node_assign_owner_action_form'.)
+ *     This function takes $context as its only parameter, and is paired with
+ *     the usual _submit function, and possibly a _validate function.
+ *   - 'triggers': An array of the events (that is, hooks) that can trigger this
+ *     action. For example: array('node_insert', 'user_update'). You can also
+ *     declare support for any trigger by returning array('any') for this value.
+ *   - 'behavior': (optional) A machine-readable array of behaviors of this
+ *     action, used to signal additionally required actions that may need to be
+ *     triggered. Currently recognized behaviors by Trigger module:
+ *     - 'changes_property': If an action with this behavior is assigned to a
+ *       trigger other than a "presave" hook, any save actions also assigned to
+ *       this trigger are moved later in the list. If no save action is present,
+ *       one will be added.
+ *       Modules that are processing actions (like Trigger module) should take
+ *       special care for the "presave" hook, in which case a dependent "save"
+ *       action should NOT be invoked.
+ *
+ * @ingroup actions
+ */
+function hook_action_info() {
+  return array(
+    'comment_unpublish_action' => array(
+      'type' => 'comment',
+      'label' => t('Unpublish comment'),
+      'configurable' => FALSE,
+      'behavior' => array('changes_property'),
+      'triggers' => array('comment_presave', 'comment_insert', 'comment_update'),
+    ),
+    'comment_unpublish_by_keyword_action' => array(
+      'type' => 'comment',
+      'label' => t('Unpublish comment containing keyword(s)'),
+      'configurable' => TRUE,
+      'behavior' => array('changes_property'),
+      'triggers' => array('comment_presave', 'comment_insert', 'comment_update'),
+    ),
+    'comment_save_action' => array(
+      'type' => 'comment',
+      'label' => t('Save comment'),
+      'configurable' => FALSE,
+      'triggers' => array('comment_insert', 'comment_update'),
+    ),
+  );
+}
+
+/**
+ * Executes code after an action is deleted.
+ *
+ * @param $aid
+ *   The action ID.
+ */
+function hook_actions_delete($aid) {
+  db_delete('actions_assignments')
+    ->condition('aid', $aid)
+    ->execute();
+}
+
+/**
+ * Alters the actions declared by another module.
+ *
+ * Called by actions_list() to allow modules to alter the return values from
+ * implementations of hook_action_info().
+ *
+ * @see trigger_example_action_info_alter()
+ */
+function hook_action_info_alter(&$actions) {
+  $actions['node_unpublish_action']['label'] = t('Unpublish and remove from public view.');
+}
+
+/**
+ * Declare archivers to the system.
+ *
+ * An archiver is a class that is able to package and unpackage one or more files
+ * into a single possibly compressed file.  Common examples of such files are
+ * zip files and tar.gz files.  All archiver classes must implement
+ * ArchiverInterface.
+ *
+ * Each entry should be keyed on a unique value, and specify three
+ * additional keys:
+ * - class: The name of the PHP class for this archiver.
+ * - extensions: An array of file extensions that this archiver supports.
+ * - weight: This optional key specifies the weight of this archiver.
+ *   When mapping file extensions to archivers, the first archiver by
+ *   weight found that supports the requested extension will be used.
+ *
+ * @see hook_archiver_info_alter()
+ */
+function hook_archiver_info() {
+  return array(
+    'tar' => array(
+      'class' => 'ArchiverTar',
+      'extensions' => array('tar', 'tar.gz', 'tar.bz2'),
+    ),
+  );
+}
+
+/**
+ * Alter archiver information declared by other modules.
+ *
+ * See hook_archiver_info() for a description of archivers and the archiver
+ * information structure.
+ *
+ * @param $info
+ *   Archiver information to alter (return values from hook_archiver_info()).
+ */
+function hook_archiver_info_alter(&$info) {
+  $info['tar']['extensions'][] = 'tgz';
+}
+
+/**
+ * Define additional date types.
+ *
+ * Next to the 'long', 'medium' and 'short' date types defined in core, any
+ * module can define additional types that can be used when displaying dates,
+ * by implementing this hook. A date type is basically just a name for a date
+ * format.
+ *
+ * Date types are used in the administration interface: a user can assign
+ * date format types defined in hook_date_formats() to date types defined in
+ * this hook. Once a format has been assigned by a user, the machine name of a
+ * type can be used in the format_date() function to format a date using the
+ * chosen formatting.
+ *
+ * To define a date type in a module and make sure a format has been assigned to
+ * it, without requiring a user to visit the administrative interface, use
+ * @code variable_set('date_format_' . $type, $format); @endcode
+ * where $type is the machine-readable name defined here, and $format is a PHP
+ * date format string.
+ *
+ * To avoid namespace collisions with date types defined by other modules, it is
+ * recommended that each date type starts with the module name. A date type
+ * can consist of letters, numbers and underscores.
+ *
+ * @return
+ *   An array of date types where the keys are the machine-readable names and
+ *   the values are the human-readable labels.
+ *
+ * @see hook_date_formats()
+ * @see format_date()
+ */
+function hook_date_format_types() {
+  // Define the core date format types.
+  return array(
+    'long' => t('Long'),
+    'medium' => t('Medium'),
+    'short' => t('Short'),
+  );
+}
+
+/**
+ * Modify existing date types.
+ *
+ * Allows other modules to modify existing date types like 'long'. Called by
+ * _system_date_format_types_build(). For instance, A module may use this hook
+ * to apply settings across all date types, such as locking all date types so
+ * they appear to be provided by the system.
+ *
+ * @param $types
+ *   A list of date types. Each date type is keyed by the machine-readable name
+ *   and the values are associative arrays containing:
+ *   - is_new: Set to FALSE to override previous settings.
+ *   - module: The name of the module that created the date type.
+ *   - type: The machine-readable date type name.
+ *   - title: The human-readable date type name.
+ *   - locked: Specifies that the date type is system-provided.
+ */
+function hook_date_format_types_alter(&$types) {
+  foreach ($types as $name => $type) {
+    $types[$name]['locked'] = 1;
+  }
+}
+
+/**
+ * Define additional date formats.
+ *
+ * This hook is used to define the PHP date format strings that can be assigned
+ * to date types in the administrative interface. A module can provide date
+ * format strings for the core-provided date types ('long', 'medium', and
+ * 'short'), or for date types defined in hook_date_format_types() by itself
+ * or another module.
+ *
+ * Since date formats can be locale-specific, you can specify the locales that
+ * each date format string applies to. There may be more than one locale for a
+ * format. There may also be more than one format for the same locale. For
+ * example d/m/Y and Y/m/d work equally well in some locales. You may wish to
+ * define some additional date formats that aren't specific to any one locale,
+ * for example, "Y m". For these cases, the 'locales' component of the return
+ * value should be omitted.
+ *
+ * Providing a date format here does not normally assign the format to be
+ * used with the associated date type -- a user has to choose a format for each
+ * date type in the administrative interface. There is one exception: locale
+ * initialization chooses a locale-specific format for the three core-provided
+ * types (see locale_get_localized_date_format() for details). If your module
+ * needs to ensure that a date type it defines has a format associated with it,
+ * call @code variable_set('date_format_' . $type, $format); @endcode
+ * where $type is the machine-readable name defined in hook_date_format_types(),
+ * and $format is a PHP date format string.
+ *
+ * @return
+ *   A list of date formats to offer as choices in the administrative
+ *   interface. Each date format is a keyed array consisting of three elements:
+ *   - 'type': The date type name that this format can be used with, as
+ *     declared in an implementation of hook_date_format_types().
+ *   - 'format': A PHP date format string to use when formatting dates. It
+ *     can contain any of the formatting options described at
+ *     http://php.net/manual/en/function.date.php
+ *   - 'locales': (optional) An array of 2 and 5 character locale codes,
+ *     defining which locales this format applies to (for example, 'en',
+ *     'en-us', etc.). If your date format is not language-specific, leave this
+ *     array empty.
+ *
+ * @see hook_date_format_types()
+ */
+function hook_date_formats() {
+  return array(
+    array(
+      'type' => 'mymodule_extra_long',
+      'format' => 'l jS F Y H:i:s e',
+      'locales' => array('en-ie'),
+    ),
+    array(
+      'type' => 'mymodule_extra_long',
+      'format' => 'l jS F Y h:i:sa',
+      'locales' => array('en', 'en-us'),
+    ),
+    array(
+      'type' => 'short',
+      'format' => 'F Y',
+      'locales' => array(),
+    ),
+  );
+}
+
+/**
+ * Alter date formats declared by another module.
+ *
+ * Called by _system_date_format_types_build() to allow modules to alter the
+ * return values from implementations of hook_date_formats().
+ */
+function hook_date_formats_alter(&$formats) {
+  foreach ($formats as $id => $format) {
+    $formats[$id]['locales'][] = 'en-ca';
+  }
+}
+
+/**
+ * Alters the delivery callback used to send the result of the page callback to the browser.
+ *
+ * Called by drupal_deliver_page() to allow modules to alter how the
+ * page is delivered to the browser.
+ *
+ * This hook is intended for altering the delivery callback based on
+ * information unrelated to the path of the page accessed. For example,
+ * it can be used to set the delivery callback based on a HTTP request
+ * header (as shown in the code sample). To specify a delivery callback
+ * based on path information, use hook_menu() or hook_menu_alter().
+ *
+ * This hook can also be used as an API function that can be used to explicitly
+ * set the delivery callback from some other function. For example, for a module
+ * named MODULE:
+ * @code
+ * function MODULE_page_delivery_callback_alter(&$callback, $set = FALSE) {
+ *   static $stored_callback;
+ *   if ($set) {
+ *     $stored_callback = $callback;
+ *   }
+ *   elseif (isset($stored_callback)) {
+ *     $callback = $stored_callback;
+ *   }
+ * }
+ * function SOMEWHERE_ELSE() {
+ *   $desired_delivery_callback = 'foo';
+ *   MODULE_page_delivery_callback_alter($desired_delivery_callback, TRUE);
+ * }
+ * @endcode
+ *
+ * @param $callback
+ *   The name of a function.
+ *
+ * @see drupal_deliver_page()
+ */
+function hook_page_delivery_callback_alter(&$callback) {
+  // jQuery sets a HTTP_X_REQUESTED_WITH header of 'XMLHttpRequest'.
+  // If a page would normally be delivered as an html page, and it is called
+  // from jQuery, deliver it instead as an Ajax response.
+  if (isset($_SERVER['HTTP_X_REQUESTED_WITH']) && $_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest' && $callback == 'drupal_deliver_html_page') {
+    $callback = 'ajax_deliver';
+  }
+}
+
+/**
+ * Alters theme operation links.
+ *
+ * @param $theme_groups
+ *   An associative array containing groups of themes.
+ *
+ * @see system_themes_page()
+ */
+function hook_system_themes_page_alter(&$theme_groups) {
+  foreach ($theme_groups as $state => &$group) {
+    foreach ($theme_groups[$state] as &$theme) {
+      // Add a foo link to each list of theme operations.
+      $theme->operations[] = array(
+        'title' => t('Foo'),
+        'href' => 'admin/appearance/foo',
+        'query' => array('theme' => $theme->name)
+      );
+    }
+  }
+}
+
+/**
+ * Alters inbound URL requests.
+ *
+ * @param $path
+ *   The path being constructed, which, if a path alias, has been resolved to a
+ *   Drupal path by the database, and which also may have been altered by other
+ *   modules before this one.
+ * @param $original_path
+ *   The original path, before being checked for path aliases or altered by any
+ *   modules.
+ * @param $path_language
+ *   The language of the path.
+ *
+ * @see drupal_get_normal_path()
+ */
+function hook_url_inbound_alter(&$path, $original_path, $path_language) {
+  // Create the path user/me/edit, which allows a user to edit their account.
+  if (preg_match('|^user/me/edit(/.*)?|', $path, $matches)) {
+    global $user;
+    $path = 'user/' . $user->uid . '/edit' . $matches[1];
+  }
+}
+
+/**
+ * Alters outbound URLs.
+ *
+ * @param $path
+ *   The outbound path to alter, not adjusted for path aliases yet. It won't be
+ *   adjusted for path aliases until all modules are finished altering it, thus
+ *   being consistent with hook_url_inbound_alter(), which adjusts for all path
+ *   aliases before allowing modules to alter it. This may have been altered by
+ *   other modules before this one.
+ * @param $options
+ *   A set of URL options for the URL so elements such as a fragment or a query
+ *   string can be added to the URL.
+ * @param $original_path
+ *   The original path, before being altered by any modules.
+ *
+ * @see url()
+ */
+function hook_url_outbound_alter(&$path, &$options, $original_path) {
+  // Use an external RSS feed rather than the Drupal one.
+  if ($path == 'rss.xml') {
+    $path = 'http://example.com/rss.xml';
+    $options['external'] = TRUE;
+  }
+
+  // Instead of pointing to user/[uid]/edit, point to user/me/edit.
+  if (preg_match('|^user/([0-9]*)/edit(/.*)?|', $path, $matches)) {
+    global $user;
+    if ($user->uid == $matches[1]) {
+      $path = 'user/me/edit' . $matches[2];
+    }
+  }
+}
+
+/**
+ * Alter the username that is displayed for a user.
+ *
+ * Called by format_username() to allow modules to alter the username that's
+ * displayed. Can be used to ensure user privacy in situations where
+ * $account->name is too revealing.
+ *
+ * @param $name
+ *   The string that format_username() will return.
+ *
+ * @param $account
+ *   The account object passed to format_username().
+ *
+ * @see format_username()
+ */
+function hook_username_alter(&$name, $account) {
+  // Display the user's uid instead of name.
+  if (isset($account->uid)) {
+    $name = t('User !uid', array('!uid' => $account->uid));
+  }
+}
+
+/**
+ * Provide replacement values for placeholder tokens.
+ *
+ * This hook is invoked when someone calls token_replace(). That function first
+ * scans the text for [type:token] patterns, and splits the needed tokens into
+ * groups by type. Then hook_tokens() is invoked on each token-type group,
+ * allowing your module to respond by providing replacement text for any of
+ * the tokens in the group that your module knows how to process.
+ *
+ * A module implementing this hook should also implement hook_token_info() in
+ * order to list its available tokens on editing screens.
+ *
+ * @param $type
+ *   The machine-readable name of the type (group) of token being replaced, such
+ *   as 'node', 'user', or another type defined by a hook_token_info()
+ *   implementation.
+ * @param $tokens
+ *   An array of tokens to be replaced. The keys are the machine-readable token
+ *   names, and the values are the raw [type:token] strings that appeared in the
+ *   original text.
+ * @param $data
+ *   (optional) An associative array of data objects to be used when generating
+ *   replacement values, as supplied in the $data parameter to token_replace().
+ * @param $options
+ *   (optional) An associative array of options for token replacement; see
+ *   token_replace() for possible values.
+ *
+ * @return
+ *   An associative array of replacement values, keyed by the raw [type:token]
+ *   strings from the original text.
+ *
+ * @see hook_token_info()
+ * @see hook_tokens_alter()
+ */
+function hook_tokens($type, $tokens, array $data = array(), array $options = array()) {
+  $url_options = array('absolute' => TRUE);
+  if (isset($options['language'])) {
+    $url_options['language'] = $options['language'];
+    $language_code = $options['language']->language;
+  }
+  else {
+    $language_code = NULL;
+  }
+  $sanitize = !empty($options['sanitize']);
+
+  $replacements = array();
+
+  if ($type == 'node' && !empty($data['node'])) {
+    $node = $data['node'];
+
+    foreach ($tokens as $name => $original) {
+      switch ($name) {
+        // Simple key values on the node.
+        case 'nid':
+          $replacements[$original] = $node->nid;
+          break;
+
+        case 'title':
+          $replacements[$original] = $sanitize ? check_plain($node->title) : $node->title;
+          break;
+
+        case 'edit-url':
+          $replacements[$original] = url('node/' . $node->nid . '/edit', $url_options);
+          break;
+
+        // Default values for the chained tokens handled below.
+        case 'author':
+          $name = ($node->uid == 0) ? variable_get('anonymous', t('Anonymous')) : $node->name;
+          $replacements[$original] = $sanitize ? filter_xss($name) : $name;
+          break;
+
+        case 'created':
+          $replacements[$original] = format_date($node->created, 'medium', '', NULL, $language_code);
+          break;
+      }
+    }
+
+    if ($author_tokens = token_find_with_prefix($tokens, 'author')) {
+      $author = user_load($node->uid);
+      $replacements += token_generate('user', $author_tokens, array('user' => $author), $options);
+    }
+
+    if ($created_tokens = token_find_with_prefix($tokens, 'created')) {
+      $replacements += token_generate('date', $created_tokens, array('date' => $node->created), $options);
+    }
+  }
+
+  return $replacements;
+}
+
+/**
+ * Alter replacement values for placeholder tokens.
+ *
+ * @param $replacements
+ *   An associative array of replacements returned by hook_tokens().
+ * @param $context
+ *   The context in which hook_tokens() was called. An associative array with
+ *   the following keys, which have the same meaning as the corresponding
+ *   parameters of hook_tokens():
+ *   - 'type'
+ *   - 'tokens'
+ *   - 'data'
+ *   - 'options'
+ *
+ * @see hook_tokens()
+ */
+function hook_tokens_alter(array &$replacements, array $context) {
+  $options = $context['options'];
+
+  if (isset($options['language'])) {
+    $url_options['language'] = $options['language'];
+    $language_code = $options['language']->language;
+  }
+  else {
+    $language_code = NULL;
+  }
+  $sanitize = !empty($options['sanitize']);
+
+  if ($context['type'] == 'node' && !empty($context['data']['node'])) {
+    $node = $context['data']['node'];
+
+    // Alter the [node:title] token, and replace it with the rendered content
+    // of a field (field_title).
+    if (isset($context['tokens']['title'])) {
+      $title = field_view_field('node', $node, 'field_title', 'default', $language_code);
+      $replacements[$context['tokens']['title']] = drupal_render($title);
+    }
+  }
+}
+
+/**
+ * Provide information about available placeholder tokens and token types.
+ *
+ * Tokens are placeholders that can be put into text by using the syntax
+ * [type:token], where type is the machine-readable name of a token type, and
+ * token is the machine-readable name of a token within this group. This hook
+ * provides a list of types and tokens to be displayed on text editing screens,
+ * so that people editing text can see what their token options are.
+ *
+ * The actual token replacement is done by token_replace(), which invokes
+ * hook_tokens(). Your module will need to implement that hook in order to
+ * generate token replacements from the tokens defined here.
+ *
+ * @return
+ *   An associative array of available tokens and token types. The outer array
+ *   has two components:
+ *   - types: An associative array of token types (groups). Each token type is
+ *     an associative array with the following components:
+ *     - name: The translated human-readable short name of the token type.
+ *     - description: A translated longer description of the token type.
+ *     - needs-data: The type of data that must be provided to token_replace()
+ *       in the $data argument (i.e., the key name in $data) in order for tokens
+ *       of this type to be used in the $text being processed. For instance, if
+ *       the token needs a node object, 'needs-data' should be 'node', and to
+ *       use this token in token_replace(), the caller needs to supply a node
+ *       object as $data['node']. Some token data can also be supplied
+ *       indirectly; for instance, a node object in $data supplies a user object
+ *       (the author of the node), allowing user tokens to be used when only
+ *       a node data object is supplied.
+ *   - tokens: An associative array of tokens. The outer array is keyed by the
+ *     group name (the same key as in the types array). Within each group of
+ *     tokens, each token item is keyed by the machine name of the token, and
+ *     each token item has the following components:
+ *     - name: The translated human-readable short name of the token.
+ *     - description: A translated longer description of the token.
+ *     - type (optional): A 'needs-data' data type supplied by this token, which
+ *       should match a 'needs-data' value from another token type. For example,
+ *       the node author token provides a user object, which can then be used
+ *       for token replacement data in token_replace() without having to supply
+ *       a separate user object.
+ *
+ * @see hook_token_info_alter()
+ * @see hook_tokens()
+ */
+function hook_token_info() {
+  $type = array(
+    'name' => t('Nodes'),
+    'description' => t('Tokens related to individual nodes.'),
+    'needs-data' => 'node',
+  );
+
+  // Core tokens for nodes.
+  $node['nid'] = array(
+    'name' => t("Node ID"),
+    'description' => t("The unique ID of the node."),
+  );
+  $node['title'] = array(
+    'name' => t("Title"),
+    'description' => t("The title of the node."),
+  );
+  $node['edit-url'] = array(
+    'name' => t("Edit URL"),
+    'description' => t("The URL of the node's edit page."),
+  );
+
+  // Chained tokens for nodes.
+  $node['created'] = array(
+    'name' => t("Date created"),
+    'description' => t("The date the node was posted."),
+    'type' => 'date',
+  );
+  $node['author'] = array(
+    'name' => t("Author"),
+    'description' => t("The author of the node."),
+    'type' => 'user',
+  );
+
+  return array(
+    'types' => array('node' => $type),
+    'tokens' => array('node' => $node),
+  );
+}
+
+/**
+ * Alter the metadata about available placeholder tokens and token types.
+ *
+ * @param $data
+ *   The associative array of token definitions from hook_token_info().
+ *
+ * @see hook_token_info()
+ */
+function hook_token_info_alter(&$data) {
+  // Modify description of node tokens for our site.
+  $data['tokens']['node']['nid'] = array(
+    'name' => t("Node ID"),
+    'description' => t("The unique ID of the article."),
+  );
+  $data['tokens']['node']['title'] = array(
+    'name' => t("Title"),
+    'description' => t("The title of the article."),
+  );
+
+  // Chained tokens for nodes.
+  $data['tokens']['node']['created'] = array(
+    'name' => t("Date created"),
+    'description' => t("The date the article was posted."),
+    'type' => 'date',
+  );
+}
+
+/**
+ * Alter batch information before a batch is processed.
+ *
+ * Called by batch_process() to allow modules to alter a batch before it is
+ * processed.
+ *
+ * @param $batch
+ *   The associative array of batch information. See batch_set() for details on
+ *   what this could contain.
+ *
+ * @see batch_set()
+ * @see batch_process()
+ *
+ * @ingroup batch
+ */
+function hook_batch_alter(&$batch) {
+  // If the current page request is inside the overlay, add ?render=overlay to
+  // the success callback URL, so that it appears correctly within the overlay.
+  if (overlay_get_mode() == 'child') {
+    if (isset($batch['url_options']['query'])) {
+      $batch['url_options']['query']['render'] = 'overlay';
+    }
+    else {
+      $batch['url_options']['query'] = array('render' => 'overlay');
+    }
+  }
+}
+
+/**
+ * Provide information on Updaters (classes that can update Drupal).
+ *
+ * An Updater is a class that knows how to update various parts of the Drupal
+ * file system, for example to update modules that have newer releases, or to
+ * install a new theme.
+ *
+ * @return
+ *   An associative array of information about the updater(s) being provided.
+ *   This array is keyed by a unique identifier for each updater, and the
+ *   values are subarrays that can contain the following keys:
+ *   - class: The name of the PHP class which implements this updater.
+ *   - name: Human-readable name of this updater.
+ *   - weight: Controls what order the Updater classes are consulted to decide
+ *     which one should handle a given task. When an update task is being run,
+ *     the system will loop through all the Updater classes defined in this
+ *     registry in weight order and let each class respond to the task and
+ *     decide if each Updater wants to handle the task. In general, this
+ *     doesn't matter, but if you need to override an existing Updater, make
+ *     sure your Updater has a lighter weight so that it comes first.
+ *
+ * @see drupal_get_updaters()
+ * @see hook_updater_info_alter()
+ */
+function hook_updater_info() {
+  return array(
+    'module' => array(
+      'class' => 'ModuleUpdater',
+      'name' => t('Update modules'),
+      'weight' => 0,
+    ),
+    'theme' => array(
+      'class' => 'ThemeUpdater',
+      'name' => t('Update themes'),
+      'weight' => 0,
+    ),
+  );
+}
+
+/**
+ * Alter the Updater information array.
+ *
+ * An Updater is a class that knows how to update various parts of the Drupal
+ * file system, for example to update modules that have newer releases, or to
+ * install a new theme.
+ *
+ * @param array $updaters
+ *   Associative array of updaters as defined through hook_updater_info().
+ *   Alter this array directly.
+ *
+ * @see drupal_get_updaters()
+ * @see hook_updater_info()
+ */
+function hook_updater_info_alter(&$updaters) {
+  // Adjust weight so that the theme Updater gets a chance to handle a given
+  // update task before module updaters.
+  $updaters['theme']['weight'] = -1;
+}
+
+/**
+ * Alter the default country list.
+ *
+ * @param $countries
+ *   The associative array of countries keyed by ISO 3166-1 country code.
+ *
+ * @see country_get_list()
+ * @see _country_get_predefined_list()
+ */
+function hook_countries_alter(&$countries) {
+  // Elbonia is now independent, so add it to the country list.
+  $countries['EB'] = 'Elbonia';
+}
+
+/**
+ * Control site status before menu dispatching.
+ *
+ * The hook is called after checking whether the site is offline but before
+ * the current router item is retrieved and executed by
+ * menu_execute_active_handler(). If the site is in offline mode,
+ * $menu_site_status is set to MENU_SITE_OFFLINE.
+ *
+ * @param $menu_site_status
+ *   Supported values are MENU_SITE_OFFLINE, MENU_ACCESS_DENIED,
+ *   MENU_NOT_FOUND and MENU_SITE_ONLINE. Any other value than
+ *   MENU_SITE_ONLINE will skip the default menu handling system and be passed
+ *   for delivery to drupal_deliver_page() with a NULL
+ *   $default_delivery_callback.
+ * @param $path
+ *   Contains the system path that is going to be loaded. This is read only,
+ *   use hook_url_inbound_alter() to change the path.
+ */
+function hook_menu_site_status_alter(&$menu_site_status, $path) {
+  // Allow access to my_module/authentication even if site is in offline mode.
+  if ($menu_site_status == MENU_SITE_OFFLINE && user_is_anonymous() && $path == 'my_module/authentication') {
+    $menu_site_status = MENU_SITE_ONLINE;
+  }
+}
+
+/**
+ * Register information about FileTransfer classes provided by a module.
+ *
+ * The FileTransfer class allows transferring files over a specific type of
+ * connection. Core provides classes for FTP and SSH. Contributed modules are
+ * free to extend the FileTransfer base class to add other connection types,
+ * and if these classes are registered via hook_filetransfer_info(), those
+ * connection types will be available to site administrators using the Update
+ * manager when they are redirected to the authorize.php script to authorize
+ * the file operations.
+ *
+ * @return array
+ *   Nested array of information about FileTransfer classes. Each key is a
+ *   FileTransfer type (not human readable, used for form elements and
+ *   variable names, etc), and the values are subarrays that define properties
+ *   of that type. The keys in each subarray are:
+ *   - 'title': Required. The human-readable name of the connection type.
+ *   - 'class': Required. The name of the FileTransfer class. The constructor
+ *     will always be passed the full path to the root of the site that should
+ *     be used to restrict where file transfer operations can occur (the $jail)
+ *     and an array of settings values returned by the settings form.
+ *   - 'file': Required. The include file containing the FileTransfer class.
+ *     This should be a separate .inc file, not just the .module file, so that
+ *     the minimum possible code is loaded when authorize.php is running.
+ *   - 'file path': Optional. The directory (relative to the Drupal root)
+ *     where the include file lives. If not defined, defaults to the base
+ *     directory of the module implementing the hook.
+ *   - 'weight': Optional. Integer weight used for sorting connection types on
+ *     the authorize.php form.
+ *
+ * @see FileTransfer
+ * @see authorize.php
+ * @see hook_filetransfer_info_alter()
+ * @see drupal_get_filetransfer_info()
+ */
+function hook_filetransfer_info() {
+  $info['sftp'] = array(
+    'title' => t('SFTP (Secure FTP)'),
+    'file' => 'sftp.filetransfer.inc',
+    'class' => 'FileTransferSFTP',
+    'weight' => 10,
+  );
+  return $info;
+}
+
+/**
+ * Alter the FileTransfer class registry.
+ *
+ * @param array $filetransfer_info
+ *   Reference to a nested array containing information about the FileTransfer
+ *   class registry.
+ *
+ * @see hook_filetransfer_info()
+ */
+function hook_filetransfer_info_alter(&$filetransfer_info) {
+  if (variable_get('paranoia', FALSE)) {
+    // Remove the FTP option entirely.
+    unset($filetransfer_info['ftp']);
+    // Make sure the SSH option is listed first.
+    $filetransfer_info['ssh']['weight'] = -10;
+  }
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */
+
+/**
+ * @addtogroup callbacks
+ * @{
+ */
+
+/**
+ * Return the URI for an entity.
+ *
+ * Callback for hook_entity_info().
+ *
+ * @param $entity
+ *   The entity to return the URI for.
+ *
+ * @return
+ *   An associative array with the following elements:
+ *   - 'path': The URL path for the entity.
+ *   - 'options': (optional) An array of options for the url() function.
+ *   The actual entity URI can be constructed by passing these elements to
+ *   url().
+ */
+function callback_entity_info_uri($entity) {
+  return array(
+    'path' => 'node/' . $entity->nid,
+  );
+}
+
+/**
+ * Return the label of an entity.
+ *
+ * Callback for hook_entity_info().
+ *
+ * @param $entity
+ *   The entity for which to generate the label.
+ * @param $entity_type
+ *   The entity type; e.g., 'node' or 'user'.
+ *
+ * @return
+ *   An unsanitized string with the label of the entity.
+ *
+ * @see entity_label()
+ */
+function callback_entity_info_label($entity, $entity_type) {
+  return empty($entity->title) ? 'Untitled entity' : $entity->title;
+}
+
+/**
+ * Return the language code of the entity.
+ *
+ * Callback for hook_entity_info().
+ *
+ * The language callback is meant to be used primarily for temporary alterations
+ * of the property value.
+ *
+ * @param $entity
+ *   The entity for which to return the language.
+ * @param $entity_type
+ *   The entity type; e.g., 'node' or 'user'.
+ *
+ * @return
+ *   The language code for the language of the entity.
+ *
+ * @see entity_language()
+ */
+function callback_entity_info_language($entity, $entity_type) {
+  return $entity->language;
+}
+
+/**
+ * @} End of "addtogroup callbacks".
+ */
+
+/**
+ * @defgroup update_api Update versions of API functions
+ * @{
+ * Functions that are similar to normal API functions, but do not invoke hooks.
+ *
+ * These simplified versions of core API functions are provided for use by
+ * update functions (hook_update_N() implementations).
+ *
+ * During database updates the schema of any module could be out of date. For
+ * this reason, caution is needed when using any API function within an update
+ * function - particularly CRUD functions, functions that depend on the schema
+ * (for example by using drupal_write_record()), and any functions that invoke
+ * hooks.
+ *
+ * Instead, a simplified utility function should be used. If a utility version
+ * of the API function you require does not already exist, then you should
+ * create a new function. The new utility function should be named
+ * _update_N_mymodule_my_function(). N is the schema version the function acts
+ * on (the schema version is the number N from the hook_update_N()
+ * implementation where this schema was introduced, or a number following the
+ * same numbering scheme), and mymodule_my_function is the name of the original
+ * API function including the module's name.
+ *
+ * Examples:
+ * - _update_6000_mymodule_save(): This function performs a save operation
+ *   without invoking any hooks using the 6.x schema.
+ * - _update_7000_mymodule_save(): This function performs the same save
+ *   operation using the 7.x schema.
+ *
+ * The utility function should not invoke any hooks, and should perform database
+ * operations using functions from the
+ * @link database Database abstraction layer, @endlink
+ * like db_insert(), db_update(), db_delete(), db_query(), and so on.
+ *
+ * If a change to the schema necessitates a change to the utility function, a
+ * new function should be created with a name based on the version of the schema
+ * it acts on. See _update_7000_bar_get_types() and _update_7001_bar_get_types()
+ * in the code examples that follow.
+ *
+ * For example, foo.install could contain:
+ * @code
+ * function foo_update_dependencies() {
+ *   // foo_update_7010() needs to run after bar_update_7000().
+ *   $dependencies['foo'][7010] = array(
+ *     'bar' => 7000,
+ *   );
+ *
+ *   // foo_update_7036() needs to run after bar_update_7001().
+ *   $dependencies['foo'][7036] = array(
+ *     'bar' => 7001,
+ *   );
+ *
+ *   return $dependencies;
+ * }
+ *
+ * function foo_update_7000() {
+ *   // No updates have been run on the {bar_types} table yet, so this needs
+ *   // to work with the 6.x schema.
+ *   foreach (_update_6000_bar_get_types() as $type) {
+ *     // Rename a variable.
+ *   }
+ * }
+ *
+ * function foo_update_7010() {
+ *    // Since foo_update_7010() is going to run after bar_update_7000(), it
+ *    // needs to operate on the new schema, not the old one.
+ *    foreach (_update_7000_bar_get_types() as $type) {
+ *      // Rename a different variable.
+ *    }
+ * }
+ *
+ * function foo_update_7036() {
+ *   // This update will run after bar_update_7001().
+ *   foreach (_update_7001_bar_get_types() as $type) {
+ *   }
+ * }
+ * @endcode
+ *
+ * And bar.install could contain:
+ * @code
+ * function bar_update_7000() {
+ *   // Type and bundle are confusing, so we renamed the table.
+ *   db_rename_table('bar_types', 'bar_bundles');
+ * }
+ *
+ * function bar_update_7001() {
+ *   // Database table names should be singular when possible.
+ *   db_rename_table('bar_bundles', 'bar_bundle');
+ * }
+ *
+ * function _update_6000_bar_get_types() {
+ *   db_query('SELECT * FROM {bar_types}')->fetchAll();
+ * }
+ *
+ * function _update_7000_bar_get_types() {
+ *   db_query('SELECT * FROM {bar_bundles'})->fetchAll();
+ * }
+ *
+ * function _update_7001_bar_get_types() {
+ *   db_query('SELECT * FROM {bar_bundle}')->fetchAll();
+ * }
+ * @endcode
+ *
+ * @see hook_update_N()
+ * @see hook_update_dependencies()
+ */
+
+/**
+ * @} End of "defgroup update_api".
+ */