Send User ID Variable With Paypal Subscribe - PhoneGap

I'm trying to tally a Paypal Subsciption to an app user (in Android).

Currently I'm using the generated Paypal subscribe button, tha开发者_运维百科t links out to the payment page.

How can I send the users ID and have it posted on success to a URL (where PHP will update the database etc) ?

Any ideas or suggestions appreciated!

Thanks!

If you have a server, on first launch of your app, contact the server to generate an ID for your app, save that ID somewhere, and use that ID to generate your PayPal button.