Paypal php脚本无法正常工作

Question

当我尝试这个脚本时，付款是成功的，但是当我重定向时，它说它已经失败了！我该怎么做！

index.php文件

    <?php
$paypal_url='https://www.sandbox.paypal.com/cgi-bin/webscr'; // Test Paypal API URL
$paypal_id='CENSORING MY PAYPAL EMAIL'; // Business email ID
?>
    <div class="btn">
    <form action="<?php echo $paypal_url ?>" method="post" name="frmPayPal1">
    <input type="hidden" name="business" value="<?php echo $paypal_id ?>">
    <input type="hidden" name="cmd" value="_xclick">
    <input type="hidden" name="item_name" value="PHPGang Payment">
    <input type="hidden" name="item_number" value="1">
    <input type="hidden" name="credits" value="510">
    <input type="hidden" name="userid" value="1">
    <input type="hidden" name="amount" value="10">
    <input type="hidden" name="no_shipping" value="1">
    <input type="hidden" name="currency_code" value="USD">
    <input type="hidden" name="handling" value="0">
    <input type="hidden" name="cancel_return" value="http://23.95.189.209/coen/test/cancel.php">
    <input type="hidden" name="return" value="http://23.95.189.209/coen/test/success.php">
    <input type="image" src="https://www.sandbox.paypal.com/en_US/i/btn/btn_buynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
    <img alt="" border="0" src="https://www.sandbox.paypal.com/en_US/i/scr/pixel.gif" width="1" height="1">
    </form> 
    </div>
</div>

<?php
$title = "PayPal Payment in PHP";
$heading = "Welcome to PayPal Payment PHP example.";
?>

success.php文件

    <?php
$item_no            = $_REQUEST['item_number'];
$item_transaction   = $_REQUEST['tx']; // Paypal transaction ID
$item_price         = $_REQUEST['amt']; // Paypal received amount
$item_currency      = $_REQUEST['cc']; // Paypal received currency type

$price = '10.00';
$currency='USD';

//Rechecking the product price and currency details
if($item_price==$price && $item_currency==$currency)
{
    echo "Successful Payment";
}
else
{
    echo "Failed Payment";
}

?>

我不确定为什么这不会起作用！ 企业电子邮件ID是我自己的，但我已经把它拿出来了。