Paypal返回动态链接？

I have a site and need to set up a return link for paypal.

The problem is that I have the return link dynamic where the user id changes based on who is logged in.

http://my-site.com/user/3/billing/done    // number 3 changes

Any advice on this?

I'm talking about the return URL that is at my paypal account setting. Not the button form...

To use a dynamic return link you'll need to pass your return URL with each transaction, just echo the id into the return input. "return" is the post value that paypal uses to return a buyer to your site after a transaction.

<input type="hidden" name="return" value="https://mysite.net/user/<?php echo $userid; ?>/billing/done">