Miniplay S2S API: Signature validation for server 2 server callbacks (PHP)

mpCallbackSignatureVerification.php

<?php
$jsonString = file_get_contents("php://input"); /* Get the RAW POST DATA */
if ( ! ( isset($_SERVER['HTTP_MINI_SIGNATURE']) 
    && $_SERVER['HTTP_MINI_SIGNATURE'] == md5("[YOUR_API_KEY]".$jsonString) )) {
    throw new Exception("Invalid signature");
}
/* the request signature has been validated! */
/* Decode the JSON string received and convert it to an associative array */
$json = json_decode($jsonString); 
?>