IPN Verification Postback to HTTPS - php

Question

My PHP code currently uses the following to Postback to PayPal. How do I update this to meet the new payment security standards coming into effect?
$req = 'cmd=_notify-validate';
foreach ($_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 ('www.paypal.com', 80, $errno, $errstr, 30);
if (!$fp)
{
//an error occurred...
}
else
{
fputs ($fp, $header . $req);
while (!feof($fp))
{
$res = fgets ($fp, 1024);
if(strcmp ($res, "VERIFIED") == 0)
{
//all is well...
}
}
}

Answer 1

To enable IPN Verification Postback to HTTPS, change your code as follows,
$fp = fsockopen( 'tls://ipnpb.paypal.com', 443, $errno, $errstr, 30);
PayPal recommends to use ipnpb.paypal.com endpoint in production environment.
Also, you need to change HTTP/1.0 to HTTP/1.1 to comply with PayPal upgrades.
The Header you need to submit,
$header = "POST /cgi-bin/webscr HTTP/1.1\r\n";
$header .= "Host: www.paypal.com\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen( $req ) . "\r\n";
$header .= "Connection: close\r\n\r\n";
For the sandbox change,
$header .= "Host: www.paypal.com\r\n";
to
$header .= "Host: www.sandbox.paypal.com\r\n";

Answer 2

The new code suggested above has now had a chance to be tested.
This did NOT work:
// 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/1.1\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
$fp = fsockopen( 'tls://ipnpb.paypal.com', 443, $errno, $errstr, 30);
This is what works:
// 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 ('www.paypal.com', 80, $errno, $errstr, 30);
What to do about using HTTP/1.0 and posting to www.paypal.com rather than using HTTP/1.1 and posting to tls://ipnpb.paypal.com?

Answer 3

There's a couple of things that need to be done:
You're still on HTTP/1.0; you need to switch to HTTP/1.1.
You need to switch to using TLS.
Most PHP setups nowadays should have cURL installed, so the easiest thing to do would be to use cURL. To do this, the last four lines of your code would change to the following:
$curl = curl_init( 'https://ipnpb.paypal.com/cgi-bin/webscr' );
curl_setopt( $curl, CURLOPT_RETURNTRANSFER, true );
curl_setopt( $curl, CURLOPT_POST, true );
curl_setopt( $curl, CURLOPT_POSTFIELDS, $req );
$response = curl_exec( $curl );
if( 'VERIFIED' == trim( $response ) ) {
// IPN verified by PayPal
}

Answer 4

I have a similiar issue with Paypal IPN verification and using this code
// post back to PayPal system to validate
// 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 ('www.paypal.com', 80, $errno, $errstr, 30);
If I understand the solution correctly, the new code should look like
// post back to PayPal system to validate
$header .= "POST /cgi-bin/webscr HTTP/1.1\r\n";
$header .= "Host: ipnpb.paypal.com\r\n";
$header .= "Connection: close\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
$fp = fsockopen( 'tls://ipnpb.paypal.com', 443, $errno, $errstr, 30);