ببخشید ، این کد callback هست که ارور میده

کد PHP:
<?php/** * Plugin Name: Sibapal Payment Module For Whmcs * Plugin URI: http://omidtak.ir * Version: 1.0 * Author: Omid Aran * Author Email: info[at]omidtak[dot]ir */ session_start();
include('../../../dbconnect.php');include('../../../includes/functions.php');include('../../../includes/gatewayfunctions.php');include('../../../includes/invoicefunctions.php');    function verify_smn($pin='',$amount='',$au='',$order_id=0,$bank_return=array()){    $params = array(        'pin'=>$pin ,        'amount'=>$amount ,        'au'=>$au ,        'order_id'=> (int) $order_id ,        'bank_return'=> ! empty($bank_return)?$bank_return:($_POST+$_GET) ,    );            $params['bank_return'] = base64_encode(json_encode($params['bank_return']));    $params = json_encode($params);            $do = curl_init();    curl_setopt($do,CURLOPT_URL,"https://sibapal.com/Eserviceapi/verify?params={$params}");    curl_setopt($do, CURLOPT_SSL_VERIFYPEER, 0);    curl_setopt($do,CURLOPT_RETURNTRANSFER,1);    curl_setopt($do, CURLOPT_CONNECTTIMEOUT, 20);    $response = curl_exec($do);    curl_close($do);    return json_decode($response,true);}
$gatewaymodule = 'smn'; 
$GATEWAY = getGatewayVariables($gatewaymodule);if (!$GATEWAY['type'])     die('Module Not Activated');     $invoiceid = $_GET['invoiceid'];$data = $_SESSION['smn'][$invoiceid];$amount = $data['amount'];$transid = $data['au'];    if(empty($data['amount']))    die('error');
$invoiceid = checkCbInvoiceID($invoiceid,$GATEWAY['name']); 
checkCbTransID($transid); $price = $amount;    $bank_return = $_POST + $_GET;        $res = verify_smn($GATEWAY['pin'],$amount,$transid,$invoiceid,$bank_return);       if($GATEWAY['Currencies']=='Rial')        $amount = $amount*10;            if (!empty($res) and $res['result']==1){     addInvoicePayment($invoiceid,$res['bank_au'],$amount,0,$gatewaymodule);     logTransaction($GATEWAY['name'],$_POST,'Successful'); } else     logTransaction($GATEWAY['name'],$_POST,'Unsuccessful');       
    $url = $CONFIG['SystemURL'].'/viewinvoice.php?id='.$invoiceid;die("<script>window.location='$url';</script>");// or header('Location: '.$url); ?>