using POST response in php - php

Question

I'm setting up a simple paypal button. When clicked, I need to write the order into my db and then redirect it via POST to paypal. The database part works just fine, however the POST to paypal doesn't.
I'm using the code by wez furlong to send a post request to the paypal server and need to process the response in order to redirect the client correctly (I need to get the location from the response).
In the end, this should behave just like a normal paypal "buy now" button, redirecting the user to paypal when clicked.
I just can't seem to get at the response and the paypal documentation is extremely vague on this. How do I extract the proper url for redirecting the client?
Any help appreciated!
Tobias

Answer 1

Here is how I implemented this functionality on my website. It is working fine:
Code to display the Paypal button:
Content += "<br/><a href='javascript:Pay();'><img src='http://www.example.com/images/paypal_checkout_button.jpg' alt='Secure payment through PayPal' border='0' /></a><br/><br/>";
Pay() is the javascript function called when the client clicks the button.
Code of function Pay()
function Pay() {
var MessageParam = "msgjson=" + JSON.encode(msgJSON) + "&invoicejson=" + JSON.encode(invoiceJSON);
var myRequest = new Request({url:"http://www.example.com/savetransaction.php", onSuccess: function(InvoiceId) {CallPayPal(InvoiceId);}}).post(MessageParam);
}
Function Pay does two things:
1 - submits the details of the transaction to a PHP script (savetransaction.php) running on the server. This script saves the transaction in a database. Note that the transaction is saved as Pending in the database. It will change to Paid once I receive confirmation from Paypal that it has been paid. Script savetransaction.php returns an invoice id number, which is the id from the database after the insert. This is the unique identifier that identifies this transaction throughout the payment process. I will send this number to paypal and it will send it back to me in the payment confirmation.
2 - onSuccess it calls function CallPayPal(InvoiceId), which will send the client to Paypal (see below).
Code of function CallPayPal(InvoideId)
function CallPayPal(InvoiceId) {
var PayPalUrl = "https://www.sandbox.paypal.com/cgi-bin/webscr?cmd=_xclick-subscriptions&business=YOURCODEHERE&lc=US&item_name=YOURITEMNAMEHERE&item_number=YOURITEMNUMBER&no_note=1&no_shipping=2&rm=1&return=URL_OF_SCRIPT_THAT_WILL_HANDLE_PAYPAL_RESPONSE&cancel_return=URL_OF_SCRIPT_THAT_WILL_BE_CALLED_IF_CLIENT_CANCEL_PAYMENT_AT_PAYPAL&src=1&a3=" + invoiceJSON.AmtSubs + "&p3=1&t3=M&currency_code=USD&bn=PP%2dSubscriptionsBF%3abtn_subscribeCC_LG%2egif%3aNonHosted";
window.open(PayPalUrl + "&invoice=" + InvoiceId,"_self");
}
You will need to change the paypal url to fit your needs. Mine is for a subscribe button. Note that I include the InvoiceId at the end. This will be received by PayPal and sent back in the response.
When the client finishes paying, Paypal will send him back to the address I included in the variable return. Paypal will append a transaction code to the url. See below the php script where I handle the return from Paypal:
Code for PayPalPDT.php
$req = 'cmd=_notify-synch';
$tx_token = $_GET['tx'];
$auth_token = "enter your own authorization token";
$req .= "&tx=$tx_token&at=$auth_token";
// 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 ('http://www.sandbox.paypal.com', 80, $errno, $errstr, 30);
// If possible, securely post back to paypal using HTTPS
// Your PHP server will need to be SSL enabled
// replace www.sandbox.paypal.com with www.paypal.com when you go live
$fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);
if (!$fp)
{
// HTTP ERROR
}
else
{
fputs ($fp, $header . $req);
// read the body data
$res = '';
$headerdone = false;
while (!feof($fp))
{
$line = fgets ($fp, 1024);
if (strcmp($line, "\r\n") == 0)
{
// read the header
$headerdone = true;
}
else if ($headerdone)
{
// header has been read. now read the contents
$res .= $line;
}
}
// parse the data
$lines = explode("\n", $res);
$keyarray = array();
if (strcmp ($lines[0], "SUCCESS") == 0)
{
for ($i=1; $i<count($lines);$i++)
{
list($key,$val) = explode("=", $lines[$i]);
$keyarray[urldecode($key)] = urldecode($val);
}
$firstname = $keyarray['first_name'];
$lastname = $keyarray['last_name'];
$itemname = $keyarray['item_name'];
$amount = $keyarray['payment_gross'];
$invoiceid = $keyarray['invoice'];
$profileid = $keyarray['subscr_id'];
// check the payment_status is Completed
// check that txn_id has not been previously processed
// check that receiver_email is your Primary PayPal email
// check that payment_amount/payment_currency are correct
// process payment
// show receipt to client
}
}
I hope this helps. Please feel free to ask follow up questions.
Good luck!

Answer 2

Use GET variables if you're using a header redirect.
For example: https://www.paypal.com/cgi-bin/webscr?cmd=_xclick&business=yourpaypalemail&amount=theamount&item_name=the%20item%20name
See also 'HTML variables for Website Payments Standard' at https://merchant.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_html_Appx_websitestandard_htmlvariables for additional variables you could use.

Answer 3

Since you need to redirect the user to PayPal, you can't do a POST from the server to make that happen.
Instead, I'd suggest you use some AJAX and intercept the button click. When the button gets clicked, your JavaScript function can call a URL on your server to write out the data, and then also send the user off to PayPal.

Answer 4

The code on wezfurlong is for having the server do a PHP post to paypal, not for redirecting the client. I think I implemented this by creating a html form that points to paypal and a javascript command to submit it, something like:
<html><body>
<form method='post' action='paypalurl'>
<input name='some required field' blah blah...>
</form>
<script>
document.forms[0].submit();
</script>
</body></html>