Can I send a variable to paypal, and have it post it back to me when payment completes?

Question

Iten_number hidden variable don't work in my application. But i found that custom hidden field works fine. Just add this field to the form, generated by paypal: <input type="hidden" name="custom" value="YOUR VALUE FROM DB"/>. After, you can read this value to identify, for example, what product have been purchased. (Java code): String custom = request.getParameter("custom");

Yes, if you send item_number, the IPN notification will include that when it posts back to you. I record a unique ID in the database when the user starts the payment process, and include that when sending them to PayPal. When the IPN comes in, that unique ID matches up with the record in the database, giving me all the info I need.

Edit Re your comment:

I expect there's a code example somewhere on the site linked above, but basically in my case I'm using a form that I POST to https://www.paypal.com/cgi-bin/webscr. Within that form are various hidden fields documented in the IPN stuff (cmd for what command to perform, business to specify your business ID, item_name for a nice description in the PayPal UI, item_number for the item number I mentioned above, etc., etc.). When IPN posts back to your IPN address, it includes various fields (such as payment_status — kind of important! &mdash and the item_number you fed in when posting to them).

Just to add to this old question...

There are option parameters that are commonly used for custom data sending through paypal.

These option tags are on0, on1, or on2 for the custom field names and os0, os1, and os2 for the custom field values.

I would send on0 with a value of "UserID" and os0 the actual ID.

These values will be represented in the IPN as follows:

os0 is represented as option_selection1

os1 is represented as option_selection2

os2 is represented as option_selection3

on0 is represented as option_name1

on1 is represented as option_name2

on2 is represented as option_name3

Here's the info on PayPal's HTML parameters

According to HTML Variables for PayPal Payments Standard you can send all the "Pass-through" variables:

item_number Pass-through variable for you to track product or service purchased or the contribution made. The value you specify is passed back to you upon payment completion. This variable is required if you want PayPal to track inventory or track profit and loss for the item the button sells.

custom Pass-through variable for your own tracking purposes, which buyers do not see. Default – No variable is passed back to you.

and

invoice Pass-through variable you can use to identify your invoice number for this purchase. Default – No variable is passed back to you.

All these pass-through variables are sent back by the IPN in the payment response info.

You just have to render your HTML template server-side and write the fields back in the HTML code like

<input type="hidden" name="item_number" value="{{ productID }}">
<input type="hidden" name="invoice_id" value="{{ invoiceID }}">
<input type="hidden" name="custom" value="{{ jsonInfo }}">

Technically the field "custom" can be a JSON encoded string if you want to handle more data like

myItemObject = {
   "customerEmail" : "[email protected]
   "customerID: "AAFF324"
}
jsonInfo = json.dumps( myItemObject )
return render_template(tmpl_name, jsonInfo=jsonInfo, productID=productID, invoiceID=invoiceID)

I finally get this answer, I want to share with all of you look:

on your HTML form put this code (this is Paypal sandbox):

form action="https://www.sandbox.paypal.com/cgi-bin/webscr?custom=YOUR_VAR" method="post"

On your PHP after the Paypal redirect to your page success: use the cm GET variable:

$example = $_GET["cm"];

I hope this URL solves your issue. As it solved mine as well. Add a custom variable to your form and then retrieve it on your success payment page. Example : <input type='hidden' name='custom' value='<?php echo $email; ?>'/>

and then retrieve it as :

 $_POST['custom']

What worked for me in 2021 is passing "custom_id" (inside the "purchase_units" array) to PayPal in my client app and checking "custom" on my backend.

Yes, it looks like PayPal renames the parameter for some reason.