110932 Simple modify of a PHP script

I need a simple modification of a php script. The php script returns search results from different search engines and displays advertising (revenue pilot, adsense, etc). I need the script modified to allow adding a tracking code (example: 12345) to the url so different advertising sources can be tracked. The tracking code will be passed as a variable in the initail url only. The tracking code should be valid for the entire duration of the visitor's session and embedded in any additional pages they visit on the site. This is quite a simple concept to code and probably would take 1-2 hours max. Script will be emailed to willing bidder/coder along with two different ways the id code can be embedded in the initial url. Project completion is one day maximum.