mime_header_encode

• Drupal 4.6
• Drupal 4.7
• Drupal 5
• Drupal 6
• Drupal 7

Versions

4.6 – 7

mime_header_encode($string)

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.

Code

includes/unicode.inc, line 224

<?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;
}
?>

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