morpheus_xor_cipher

//$key is of fixed length = 8

function xor_cipher($msg, $key) {
        if (empty($key)) return $msg;

        $ret = '';

        for($j = 0; $j < strlen($msg); $j++)
        {
            $ret .= chr(ord($msg[$j]) ^ ord($key[$j%strlen($key)]));
        }

        return $ret;
}