Dieser Codeschnippsel wandelt einen String nach RFC-2047 um.

Die RFC-2047 wird verwendet, um Umlaute in Mail- und News-Headern darzustellen. Die folgenden beiden Funktionen wandeln einen String entsprechend um.

/**
 * Converts the passed string to an RFC-2047 encoded word.
 * 
 * The string will always be converted. This function also takes care of
 * proper wrapping.
 *
 * @param   $str      String to be encoded
 * @param   $encode   The character set to be used (e.g. "ISO-8859-1")
 * @return  Converted string
 */
function rfc2047conv($str, $encode) {
  if(!strlen($str)) return "";
  $result  = "=?${encode}?Q?";
  $intro   = strlen($result);
  $charcnt = $intro;
  for($ix=0; $ix < strlen($str); $ix++) {
    if($charcnt > 70) {
      $result .= "?=\r\n =?${encode}Q?";
      $charcnt = $intro;
    }
    $chr = $str{$ix};
    if($chr=='?' || $chr=='_' || $chr=='=' || $chr<' ' || $chr>'~' ) {
      $result .= sprintf("=%02X", ord($chr));
      $charcnt+=3;
    }else {
      $result .= ($chr==' ' ? "_" : $chr);
      $charcnt++;
    }
  }
  $result .= "?=";
  return $result;
}

/**
 * This function will only encode the shortest required section of
 * the string. If there are no characters in the string that need to
 * be encoded, the string will be returned unaltered.
 * 
 * WARNING: Even though most mail clients can handle the result, it
 * is not RFC compliant!
 *
 * @param   $str      String to be encoded
 * @param   $encode   The character set to be used
 * @return  Converted string
 */
function rfc2047short($str, $encode) {
  return preg_replace(
    '/^([ -~]*)(.*?)([ -~]*)$/e',
    '"$1".rfc2047conv("$2",$encode)."$3"',
    $str
  );
}