Simple PHP Project - Passing URL Paramaters

This is a very simple PHP project. I need to pass some parameters from the URL on my site all the way to the shopping cart. Say, someone comes to my site with an affiliate ID: [login to view URL]**?****aff_id=111111** I wanted to be able to: 1. Set a cookie for this, so that if that person visits my site up to 30 days later my affiliate still gets paid. 2. Hide the URL, so [login to view URL] becomes just [login to view URL] after the link is clicked 3. Pass the parameter to the order page. So that when the visitor clicks on the 'Order now Button' they get redirected to: [login to view URL]**aff_id=****111111**