paypal ipn listener错误

I'm implementing an IPN listener for Paypal Adaptive Payments, I downloaded the sample code from here:

https://cms.paypal.com/cms_content/IT/it_IT/files/developer/IPN_PHP_41.txt

Then I made a transaction (with sandbox) but I think the sample is wrong because the code returns some errors in my error_log file:

[16-Jun-2013 16:11:34 UTC] PHP Warning:  stripslashes() expects parameter 1 to be string, array given in /var/www/actions/IPNListener.php on line 7
[16-Jun-2013 16:11:34 UTC] PHP Notice:  Undefined variable: header in /var/www/actions/IPNListener.php on line 12
[16-Jun-2013 16:11:34 UTC] PHP Notice:  Undefined index: item_name in /var/www/actions/IPNListener.php on line 18

The Undefined index is not only "item_name" but ALL INDEXES!!!!!

The transaction works correctly and the IPN is called by paypal automatically after the transaction...but the paypal sample code does not work at all! Do you know how to fix it?

Try this one

<?php
//Build the data to post back to Paypal
$postback = 'cmd=_notify-validate'; 

// go through each of the posted vars and add them to the postback variable
foreach ($_POST as $key => $value) {
   $value = urlencode(stripslashes($value));
   $postback .= "&$key=$value";
}

// build the header string to post back to PayPal system to validate
$header = "POST /cgi-bin/webscr HTTP/1.0
";
$header .= "Content-Type: application/x-www-form-urlencoded
";
$header .= "Content-Length: " . strlen($postback) . "

";

// Send to paypal or the sandbox depending on whether you're live or developing
// comment out one of the following lines
//$fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);//open the connection
$fp = fsockopen ('ssl://www.paypal.com', 443, $errno, $errstr, 30);
// or use port 443 for an SSL connection
//$fp = fsockopen ('ssl://www.paypal.com', 443, $errno, $errstr, 30);

    if (!$fp) 
    {
        // HTTP ERROR Failed to connect
        //error handling
    }
    else // if we've connected OK
    {
        fputs ($fp, $header . $postback);//post the data back
        while (!feof($fp)) 
        {
            $response = fgets ($fp, 1024);

            if (strcmp ($response, "VERIFIED") == 0) //It's verified
            {
                //do something
            }
            else if (strcmp ($response, "INVALID") == 0) 
            { 
                //the Paypal response is INVALID, not VERIFIED
                // This implies something is wrong
            }
        } //end of while
        fclose ($fp);
    }
?>