Mine

function crc16($string) {  $crc = 0xFFFF;  for ($x = 0; $x < strlen ($string); $x++) {   $crc = $crc ^ ord($string[$x]);   for ($y = 0; $y < 8; $y++) {     if (($crc & 0x0001) == 0x0001) {       $crc = (($crc >> 1) ^ 0xA001);     } else { $crc = $crc >> 1; }   }  }  return $crc;}