Not receiving a response from Paypal IPN Sandbox

Question

I'm putting a paypal checkout onto my website but am falling down with the listener. For those of you who are unfamiliar with the Paypal IPN system, basically Paypal sends your script with a message about the transaction, which you send back with a couple of bits added. If Paypal receives the correct reply, it'll reply with 'VERIFIED', and if not it'll say 'INVALID'.

I've succeeded with the first bit. My code is able to receive the info from paypal, add on the extras and post it back. However, I get no response from the Sandbox saying either 'VERIFIED' or 'INVALID'. I've pretty much copied my code from the paypal website so I was hoping this was going to be fairly straightforward, so if you could take a minute to look at my code, perhaps some new eyes could pick out where I've gone wrong.

Here's the code. Nothing special, it literally just gets the info, adjusts it, passes it back and reads the response (which it either isn't getting or doesn't realise it's getting)

<?php

$debug=true;

//Put together postback info

$postback = 'cmd=_notify-validate';

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

// build the header string to post back to PayPal system to validate
$header = "POST /cgi-bin/webscr HTTP/1.1\r\n";
$header .= "Host: www.sandbox.paypal.com\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen($postback) . "\r\n\r\n";

$fp = fsockopen ('www.sandbox.paypal.com', 80, $errno, $errstr, 30);//open the connection

if(!$fp){ //no conn
    die();
}

//post data back
fputs($fp, $header . $postback);

while(!feof($fp)){

    $res=fgets ($fp, 1024);

    if((strcmp($res, "VERIFIED")) == 0){ //verified!
        if($debug){         
            $filename = 'debug/debug5_verified.txt'; //create a file telling me we're verified
            $filehandle=fopen($filename, 'w');
            fwrite($filehandle,'VERIFIED!');
            fclose($filehandle);
        }
    }
}

?>

Thanks in advance!

Answer 1

Switch over to using the HTTPS url, I'm not sure when but recently all of my test scripts started failing on the plain HTTP version. They look to be migrating over.

I'm using the same paypal sample code you are:

    $fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);    

or

    $fp = fsockopen ('ssl://www.paypal.com', 443, $errno, $errstr, 30);