- bin2hex: documentation ( source)
- pack: documentation ( source)
<?php
$aux="133457799BBCDFF1";
$xorR="0123456789ABCDEF";
$key = pack('H*', $aux);
$data = pack('H*', $xorR);
$aux=bin2hex(mcrypt_encrypt(MCRYPT_DES, $key, $data, MCRYPT_MODE_ECB));
echo $aux;