Shopify incoming request verification

gistfile1.aw

<?php
	// All requests/redirects from Shopify include a signature parameter that can be used to verify the origin of the request.
	function is_valid_request($query_params, $shared_secret)
	{
		$seconds_in_a_day = 24 * 60 * 60;
		$older_than_a_day = $query_params['timestamp'] < (time() - $seconds_in_a_day);
		if ($older_than_a_day) return false;

		$signature = $query_params['signature'];
		unset($query_params['signature']);

		foreach ($query_params as $key=>$val) $params[] = "$key=$val";
		sort($params);

		return (md5($shared_secret.implode('', $params)) === $signature);
	}
?>