песочница PayPal отвечает на неверный запрос

У меня есть следующая HTML-форма

У меня была упомянутый URL возврата как http://developwithus.com/wedding/return.php на котором (я загрузил это с: https://cms.paypal.com/cms_content/US/en_US/files/developer/IPN_PHP_41.txt и добавил

');
print_r($_POST);
// read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-validate';

foreach ($_POST as $key => $value) {
    $value = urlencode(stripslashes($value));
    $req .= "&$key=$value";
}

// post back to PayPal system to validate
$header .= "POST /cgi-bin/webscr HTTP/1.0\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
$fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);

// assign posted variables to local variables
$item_name = $_POST['item_name'];
$item_number = $_POST['item_number'];
$payment_status = $_POST['payment_status'];
$payment_amount = $_POST['mc_gross'];
$payment_currency = $_POST['mc_currency'];
$txn_id = $_POST['txn_id'];
$receiver_email = $_POST['receiver_email'];
$payer_email = $_POST['payer_email'];

if (!$fp) {
// HTTP ERROR
    echo "HTTP Error";
} else {
    fputs ($fp, $header . $req);
    while (!feof($fp)) {
        $res = fgets ($fp, 1024);
        echo $res;
        if (strcmp ($res, "VERIFIED") == 0) {
            // check the payment_status is Completed
            // check that txn_id has not been previously processed
            // check that receiver_email is your Primary PayPal email
            // check that payment_amount/payment_currency are correct
            // process payment
            echo("verified");
        }
        else if (strcmp ($res, "INVALID") == 0) {
            // log for manual investigation
            echo ("invalid");
        }
    }
    fclose ($fp);
}
echo "end";
?>

но я получил неверный запрос в качестве ответа, если я перейду на счет песочницы PayPal и произведу оплату и вернусь обратно.

Array
(
   [CONTEXT] => wtgSziM4C5x0SI-9CmKcv2vkSeTLK5P_g6HqzC__YTYkcqziFNcB84p79Ja
   [myAllTextSubmitID] => 
   [cmd] => _flow
   [mc_gross] => 100.00
   [protection_eligibility] => Ineligible
   [address_status] => confirmed
   [payer_id] => Z5NWSYYVZW268
   [tax] => 0.00
   [address_street] => 1 Main St
   [payment_date] => 09:04:08 May 14, 2011 PDT
   [payment_status] => Pending
   [charset] => windows-1252
   [address_zip] => 95131
   [first_name] => Test
   [address_country_code] => US
   [address_name] => Test User
   [notify_version] => 3.1
   [custom] => 
   [payer_status] => verified
   [address_country] => United States
   [address_city] => San Jose
   [quantity] => 1
   [payer_email] => sujeet_1302606445_per@gmail.com
   [verify_sign] => AozIjtjfCe0jUnbJpR4qPrW54olKAq.SrnEktGSocrk8yYv4bpR4lJX7
   [txn_id] => 3HG58230W32603443
   [payment_type] => instant
   [last_name] => User
   [address_state] => CA
   [receiver_email] => vbnetdiscuss@yahoo.com
   [pending_reason] => unilateral
   [txn_type] => web_accept
   [item_name] => Wedding Gift
   [mc_currency] => EUR
   [item_number] => 
   [residence_country] => US
   [test_ipn] => 1
   [transaction_subject] => Wedding Gift
   [handling_amount] => 0.00
   [payment_gross] => 
   [shipping] => 0.00
   [merchant_return_link] => click here
   [form_charset] => UTF-8
)
HTTP/1.1 400 Bad Request
Date: Sat, 14 May 2011 16:05:20 GMT
Server: Apache
Set-Cookie: c9MWDuvPtT9GIMyPc3jwol1VSlO=%7cgA9mW0Yh7-iBp435VBDwyCqtOtnlE8KAk8fT_sjGXHGx2mDzXgFit5ZdHd3BOOEUt_UDRW%7cRD1g8aAyLevIAP-u4WfCokEQkimrkpQk6v6rLZ_xD-pT1ATWuv5RtcK3NIbPPwfF1cXq3G%7c; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: cookie_check=yes; expires=Tue, 11-May-2021 16:05:20 GMT; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: Apache=10.191.196.11.9095130538912094; path=/; expires=Fri, 31-Mar-05 09:37:04 GMT
Connection: close
Content-Type: text/plain; charset=ISO-8859-1

вы можете сказать мне, что я делаю не так? НЕВЕРНЫЙ ответ работает