31     public function encodeString($string, $firstLineOffset = 0, $maxLineLength = 0)
 
   33         if (0 >= $maxLineLength || 76 < $maxLineLength) {
 
   37         $encodedString = base64_encode($string);
 
   40         if (0 != $firstLineOffset) {
 
   42                 $encodedString, 0, $maxLineLength - $firstLineOffset
 
   44             $encodedString = substr(
 
   45                 $encodedString, $maxLineLength - $firstLineOffset
 
   49         return $firstLine.trim(chunk_split($encodedString, $maxLineLength, 
"\r\n"));