- var_dump: documentation ( source)
- hash_hmac: documentation ( source)
<?php
const APP_SECRET = 'ZlS7Mvj481jQNcjdWppl6kZ0^G7t2hjxxyFUVICz8xoMV4+j4k';
$auth_string = '18288821#2013-05-13 07:07:52';
$auth_hash = hash_hmac('sha256', $auth_string, APP_SECRET);
var_dump($auth_hash);