Looking for the best way to track sales by affiliates..

Not too sure if this is the right place for this request. Sorry if I'm out of topic... Please point me in the right direction if I am. I've just upgraded to php4, and it looks VERY nice. Yet to come to grips with ZEND... However, what I am looking at, is the best way to track sales by affiliates.. Say I have an affiliate called NERKS001, and his code page carries that code to my site every time someone - or that person - connects. I guess it needs a number of logs, or one log with different fields, to track the number of contacts for that code (nerks001), and the number of confirmed sales for that code. One needs I think at least those, actual times the code has been used in a connection, and the number of sales made as a result of references by that code. Oh, and also one would need to log accesses and sales where no affiliate/code was attached. Those times where people surfing the net came to the site. Has anyone done anyting along these lines? There are thousands of 'affiliate' programs out there, so it can't be all that difficult, but I'm having a bit of a struggle with the passing along of the affiliates code, especially where it leads to a sale. And, what about those times wher a user halts a sale, and then comes back to it later... hmmm - it could get a little complex. Anyway, if someone has a few pointers, I'd really appreciate it, and I'll make a start to see if I can put something together. maybe using the "sessions" thingy. thansk for any clues Robert http://www.chalmers.com.au Clipart And Books Art, Design and Graphics.