mime_header_encode

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Definition

mime_header_encode($string)
includes/common.inc, line 1757

Description

Encodes MIME/HTTP header values that contain non-ASCII, UTF-8 encoded characters.

For example, mime_header_encode('tést.txt') returns "=?UTF-8?B?dMOpc3QudHh0?=".

See http://www.rfc-editor.org/rfc/rfc2047.txt for more information.

Notes:

• Only encode strings that contain non-ASCII characters.
• We progressively cut-off a chunk with truncate_utf8(). This is to ensure each chunk starts and ends on a character boundary.
• Using \n as the chunk separator may cause problems on some systems and may have to be changed to \r\n or \r.

Related topics

Name	Description
Input validation	Functions to validate user input.

Code

<?php
function mime_header_encode($string) {
  if (preg_match('/[^\x20-\x7E]/', $string)) {
    $chunk_size = 47; // floor((75 - strlen("=?UTF-8?B??=")) * 0.75);
    $len = strlen($string);
    $output = '';
    while ($len > 0) {
      $chunk = truncate_utf8($string, $chunk_size);
      $output .= ' =?UTF-8?B?'. base64_encode($chunk) ."?=\n";
      $c = strlen($chunk);
      $string = substr($string, $c);
      $len -= $c;
    }
    return trim($output);
  }
  return $string;
}
?>