<?php
$signature1 = hash_hmac('SHA256', "st=1453362060~exp=1453363260~acl=/*", chr(63));
$signature2 = hash_hmac('SHA256', "st=1453362060~exp=1453363260~acl=/*", chr(63) . chr(23));
$signature3 = hash_hmac('SHA256', "st=1453362060~exp=1453363260~acl=/*", chr(63) . chr(23) . chr(253));
echo $signature1. "\n";
echo $signature2. "\n";
echo $signature3. "\n";
?>