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

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