Paypal ipn问题，url格式错误(沙箱工作，Paypal不)

我有一个在沙箱中完美工作的IPN文件。它返回是否有效，并正确执行代码。但是，如果我尝试实时支付，它会告诉我url是畸形的

这是实时支付的错误:

bool(false) string(15) " malformed" 

这是我的curl代码:

if($testmode === true)
{
    $paypalaction = "https://www.sandbox.paypal.com/cgi-bin/webscr";
}
elseif($paypal == "paypal")
{
    $paypalaction = "https://www.paypal.com/cgi-bin/webscr";
}
// read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-validate';
foreach ($_POST as $key => $value)
{
   // If magic quotes is enabled strip slashes
   if (get_magic_quotes_gpc())
   {
       $_POST[$key] = stripslashes($value);
       $value = stripslashes($value);
   }
   $value = urlencode($value);
   // Add the value to the request parameter
   $req .= "&$key=$value";
}
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$paypalaction); 
curl_setopt($ch, CURLOPT_FAILONERROR, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_TIMEOUT, 3);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
$res = curl_exec($ch);
var_dump($res);
var_dump(curl_error($ch));
curl_close($ch);