Chris@17: <?php
Chris@17: 
Chris@17: namespace Drupal\Component\Utility;
Chris@17: 
Chris@17: /**
Chris@17:  * Provides helpers to ensure emails are compliant with RFCs.
Chris@17:  *
Chris@17:  * @ingroup utility
Chris@17:  */
Chris@17: class Mail {
Chris@17: 
Chris@17:   /**
Chris@17:    * RFC-2822 "specials" characters.
Chris@17:    */
Chris@17:   const RFC_2822_SPECIALS = '()<>[]:;@\,."';
Chris@17: 
Chris@17:   /**
Chris@17:    * Return a RFC-2822 compliant "display-name" component.
Chris@17:    *
Chris@17:    * The "display-name" component is used in mail header "Originator" fields
Chris@17:    * (From, Sender, Reply-to) to give a human-friendly description of the
Chris@17:    * address, i.e. From: My Display Name <xyz@example.org>. RFC-822 and
Chris@17:    * RFC-2822 define its syntax and rules. This method gets as input a string
Chris@17:    * to be used as "display-name" and formats it to be RFC compliant.
Chris@17:    *
Chris@17:    * @param string $string
Chris@17:    *   A string to be used as "display-name".
Chris@17:    *
Chris@17:    * @return string
Chris@17:    *   A RFC compliant version of the string, ready to be used as
Chris@17:    *   "display-name" in mail originator header fields.
Chris@17:    */
Chris@17:   public static function formatDisplayName($string) {
Chris@17:     // Make sure we don't process html-encoded characters. They may create
Chris@17:     // unneeded trouble if left encoded, besides they will be correctly
Chris@17:     // processed if decoded.
Chris@17:     $string = Html::decodeEntities($string);
Chris@17: 
Chris@17:     // If string contains non-ASCII characters it must be (short) encoded
Chris@17:     // according to RFC-2047. The output of a "B" (Base64) encoded-word is
Chris@17:     // always safe to be used as display-name.
Chris@17:     $safe_display_name = Unicode::mimeHeaderEncode($string, TRUE);
Chris@17: 
Chris@17:     // Encoded-words are always safe to be used as display-name because don't
Chris@17:     // contain any RFC 2822 "specials" characters. However
Chris@17:     // Unicode::mimeHeaderEncode() encodes a string only if it contains any
Chris@17:     // non-ASCII characters, and leaves its value untouched (un-encoded) if
Chris@17:     // ASCII only. For this reason in order to produce a valid display-name we
Chris@17:     // still need to make sure there are no "specials" characters left.
Chris@17:     if (preg_match('/[' . preg_quote(Mail::RFC_2822_SPECIALS) . ']/', $safe_display_name)) {
Chris@17: 
Chris@17:       // If string is already quoted, it may or may not be escaped properly, so
Chris@17:       // don't trust it and reset.
Chris@17:       if (preg_match('/^"(.+)"$/', $safe_display_name, $matches)) {
Chris@17:         $safe_display_name = str_replace(['\\\\', '\\"'], ['\\', '"'], $matches[1]);
Chris@17:       }
Chris@17: 
Chris@17:       // Transform the string in a RFC-2822 "quoted-string" by wrapping it in
Chris@17:       // double-quotes. Also make sure '"' and '\' occurrences are escaped.
Chris@17:       $safe_display_name = '"' . str_replace(['\\', '"'], ['\\\\', '\\"'], $safe_display_name) . '"';
Chris@17: 
Chris@17:     }
Chris@17: 
Chris@17:     return $safe_display_name;
Chris@17:   }
Chris@17: 
Chris@17: }