- hash_hmac: documentation ( source)
- base64_encode: documentation ( source)
<?php
$input = 'POST
6d1e7cda96edddf46543c38f49ab9f88
Wed, 18 Jun 2014 09:09:38 GMT';
$key = 'JDDPv7JsROudGGIDEodj1yAuyiKxHOJjGRp2ytdNqTrjqiWLpCAew0Qamo4w/0JmicUO7NB+TdECG7AHNacPFNvhO0mWoXxhik57/hvQ6BRIa/RdQfRECA78HOd7WDqZ';
$hmac = hash_hmac('sha512', $input, $key, true); // true voor binary output
echo base64_encode($hmac);