- hex2bin: documentation ( source)
- base64_decode: documentation ( source)
- strrev: documentation ( source)
<?php
$secret = "3d3d516343746d4d6d6c315669563362";
// original method was base64 encode -> strrev -> bin2hex
// new method will be hex2bin -> strrev -> base64 decode
echo base64_decode(strrev(hex2bin($secret)));
?>