<form action="https://sandBox.paypal.com/cgi-bin/webscr" method="post" id="paypalpost" name="paypalpost">
                <input type="hidden" name="rm" value="2"/>
                <input type="hidden" name="cmd" value="_xclick">
                <input type="hidden" name="business" value="vbnetdiscuss@yahoo.com">
                <input type="hidden" name="item_name" value="Wedding Gift">
                <input type="hidden" name="currency_code" value="EUR">
                <input type="hidden" name="amount" value="<?PHP echo $value['total'];?>">
                <input type="hidden" name="return" value="http://developwithus.com/wedding/return.PHP">
                <input type="hidden" name="cancel_return" value="http://developwithus.com/wedding/return.PHP?status=0">


            <input onclick="return submitatoc();" disabled type="submit" name="submit" id="pay" class="buttonBlueBg" value="Checkout" style="cursor:pointer;">

            </form>

我曾提到返回URL为http://developwithus.com/wedding/return.php
其中,(我从https://cms.paypal.com/cms_content/US/en_US/files/developer/IPN_PHP_41.txt下载了这个并添加

<?PHP 
print_r('<pre>');
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";
?>

但是我得到了Bad Request作为回复,如果我去paypal沙盒帐户并付款并退回.

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

你能告诉我我做错了吗？
INVALID响应有效