Reikia pagabos del paysera callback

Senas kodas:

<?php

include_once '../../wcore/core.php';


if (isset($_POST['id_shop']) && is_numeric($_POST['id_shop']) && isset($_POST['id_bill']) && is_numeric($_POST['id_bill']) && isset($_POST['summa']) && is_numeric($_POST['summa']) && isset($_POST['hash']))
{
$sql=mysql_query("SELECT * FROM `worldkassa` WHERE `id_bill` = '".$_POST['id_bill']."'");
if (mysql_num_rows($sql)>0)
	{
	$data=mysql_fetch_assoc($sql);
	if ($_POST['summa']<$data['summa'])
		{
		//...
		}
		elseif($_POST['hash']!=md5($hash.$id_shop.$_POST['id_bill'].$_POST['summa']))
		{
		//...
		}
		else
		{
		mysql_query("UPDATE `worldkassa` SET `time_oplata` = '".time()."' WHERE `id` = '".$data['id']."'");
		mysql_query("UPDATE `users` SET `bits` = `bits`+'".$data['summa']."' WHERE `id` = '".$data['id_user']."'");
		mysql_query("INSERT INTO `logs_bill` (`id_user`, `time`, `razd`, `text`) values('$data[id_user]', '".time()."', 'Пополнил счет на ".$data['summa']." - ', 'Пользователь #ID - ".$data['id_user']."')"); // Записуем лог

		}
	}
}
?>

paysera callback:

<?php

require_once('WebToPay.php');

try {
   $response = WebToPay::checkResponse($_GET, array(
       'projectid'     => 0,
       'sign_password' => 'd41d8cd98f00b204e9800998ecf8427e',
   ));

   if ($response['test'] !== '0') {
       throw new Exception('Testing, real payment was not made');
   }
   if ($response['type'] !== 'macro') {
       throw new Exception('Only macro payment callbacks are accepted');
   }

   $orderId = $response['orderid'];
   $amount = $response['amount'];
   $currency = $response['currency'];
   //@todo: patikrinti, ar užsakymas su $orderId dar nepatvirtintas (callback gali būti pakartotas kelis kartus)
   //@todo: patikrinti, ar užsakymo suma ir valiuta atitinka $amount ir $currency
   //@todo: patvirtinti užsakymą

   echo 'OK';
} catch (Exception $e) {
   echo get_class($e) . ': ' . $e->getMessage();
} 

Gal kas turite minciu kaip pritaikyti sena koda prie paysera callback?