- gmdate: documentation ( source)
- md5: documentation ( source)
<?php
$apikey = 'n2ye7pb8727q7yq4mmujfb5j';
$secret = '9VXY3mfsudRqaPkn6Y6XppGK';
$timestamp = gmdate('U', 1200603038);
$sig = md5($apikey . $secret . $timestamp);
echo "$sig\n";