- hash_hmac: documentation ( source)
<?php
$string = "POST\n/\n132fbf95-d58e-f9ed-86e8-48b76f901d91\nda390885-e72f-4a93-be7f-a90220bac5c7\n/provision/provision\n132fc751-9325-63d3-a605-f74e0c25192a\n2013-10-23T15:39:34.462Z\n{\"instance-id\":\"132fc751-9325-63d3-a605-f74e0c25192a\"}";
$secret = "97cfac6e-b061-4007-a03e-eb4bc199e620";
$sig = hash_hmac('sha256', $string, $secret);
echo $sig;