PayPal, передавая item_number из PayPal в мой сценарий

Я использую Paypal Standard и пытаюсь получить item_number (в данном случае он уникален) из PayPal после успешного завершения транзакции. Я могу передать его Paypal без проблем, я вижу это отображается во время транзакции. Я использую следующий код, когда транзакция завершается. Может кто-нибудь показать мне, что мне нужно сделать, чтобы отобразить номер _number на странице «Успех» — см. Пример успеха ниже.

<?php
require_once("library.php"); // include the library file
define('EMAIL_ADD', '[email protected]'); // define any notification email
define('PAYPAL_EMAIL_ADD', '[email protected]'); // facilitator email which will receive payments change this email to a live paypal account id when the site goes live
require_once("paypal_class.php");
$p              = new paypal_class(); // paypal class
$p->admin_mail  = EMAIL_ADD; // set notification email
$action         = $_REQUEST["action"];

switch($action){
case "process": // case process insert the form data in DB and process to the paypal
mysql_query("INSERT INTO `purchases` (`invoice`, `product_id`, `product_name`, `product_quantity`, `product_amount`, `payer_fname`, `payer_lname`, `payer_address`, `payer_city`, `payer_state`, `payer_zip`, `payer_country`, `payer_email`, `payment_status`, `posted_date`) VALUES ('".$_POST["invoice"]."', '".$_POST["product_id"]."', '".$_POST["product_name"]."', '".$_POST["product_quantity"]."', '".$_POST["product_amount"]."', '".$_POST["payer_fname"]."', '".$_POST["payer_lname"]."', '".$_POST["payer_address"]."', '".$_POST["payer_city"]."', '".$_POST["payer_state"]."', '".$_POST["payer_zip"]."', '".$_POST["payer_country"]."', '".$_POST["payer_email"]."', 'pending', NOW())");
$this_script = 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'];
$p->add_field('business', PAYPAL_EMAIL_ADD); // Call the facilitator eaccount
$p->add_field('cmd', $_POST["cmd"]); // cmd should be _cart for cart checkout
$p->add_field('upload', '1');
$p->add_field('return', $this_script.'?action=success'); // return URL after the transaction got over
$p->add_field('cancel_return', $this_script.'?action=cancel'); // cancel URL if the trasaction was cancelled during half of the transaction
$p->add_field('notify_url', $this_script.'?action=ipn'); // Notify URL which received IPN (Instant Payment Notification)
$p->add_field('currency_code', $_POST["currency_code"]);
$p->add_field('invoice', $_POST["invoice"]);
$p->add_field('item_name_1', $_POST["product_name"]);
$p->add_field('item_number_1', $_POST["product_id"]);
$p->add_field('quantity_1', $_POST["product_quantity"]);
$p->add_field('amount_1', $_POST["product_amount"]);
$p->add_field('first_name', $_POST["payer_fname"]);
$p->add_field('last_name', $_POST["payer_lname"]);
$p->add_field('address1', $_POST["payer_address"]);
$p->add_field('city', $_POST["payer_city"]);
$p->add_field('state', $_POST["payer_state"]);
$p->add_field('country', $_POST["payer_country"]);
$p->add_field('zip', $_POST["payer_zip"]);
$p->add_field('night_phone_b', $_POST["phone"]);
$p->add_field('email', $_POST["payer_email"]);
$p->submit_paypal_post(); // POST it to paypal
//$p->dump_fields(); // Show the posted values for a reference, comment this line before app goes live
break;

case "success": // success case to show the user payment got success
$i=$_GET['item_number'];
echo '<title>Payment Done Successfully</title>';
echo '<center><h1> Thank You for your purchase!</h1>';
echo '<div class="as_wrapper">';
echo "<h1>Click the image below to immediately download your stencil</h1>";
echo '<br><br>';
echo '<p>This file is a PDF. You will find it in your downloads folder. The filename will start with the word <b>stencil</b>. You can search for the word <b>stencil</b></p>';
echo $i ; //Display item_number here
echo '</center>';
break;

case "cancel": // case cancel to show user the transaction was cancelled
echo "<h1>Transaction Cancelled";
break;

case "ipn": // IPN case to receive payment information. this case will not displayed in browser. This is server to server communication. PayPal will send the transactions each and every details to this case in secured POST menthod by server to server.
$trasaction_id  = $_POST["txn_id"];
$payment_status = strtolower($_POST["payment_status"]);
$invoice        = $_POST["invoice"];
$log_array      = print_r($_POST, TRUE);
$log_query      = "SELECT * FROM `paypal_log` WHERE `txn_id` = '$trasaction_id'";
$log_check      = mysql_query($log_query);
if(mysql_num_rows($log_check) <= 0){
mysql_query("INSERT INTO `paypal_log` (`txn_id`, `log`, `posted_date`) VALUES ('$trasaction_id', '$log_array', NOW())");
}else{
mysql_query("UPDATE `paypal_log` SET `log` = '$log_array' WHERE `txn_id` = '$trasaction_id'");
} // Save and update the logs array
$paypal_log_fetch   = mysql_fetch_array(mysql_query($log_query));
$paypal_log_id      = $paypal_log_fetch["id"];
if ($p->validate_ipn()){ // validate the IPN, do the others stuffs here as per your app logic
mysql_query("UPDATE `purchases` SET `trasaction_id` = '$trasaction_id ', `log_id` = '$paypal_log_id', `payment_status` = '$payment_status' WHERE `invoice` = '$invoice'");
$subject = 'Instant Payment Notification - Recieved Payment';
$p->send_report($subject); // Send the notification about the transaction
}else{
$subject = 'Instant Payment Notification - Payment Fail';
$p->send_report($subject); // failed notification
}
break;
}
?>