Visitor tracking...

Hi All, Couple questions on logic and perhaps a useable solution to visitor tracking. My firm has redesigned a site for a cliet. In this new site we are also exploring some Search Engine placement and bidding techniques to seriously bolster his activity and buying potential from WEB-referred visitors. Now.. In doing this... We'll want to setup cookies, etc to track where visitors are coming from and what Se's with what keywords are being used and if they go on to purchase a product. My Web Analysis software can, to an extent, do some of this obviously but the correlation between a purchase and a referred visitor I don't think so. Does anyone have some ideas on a quick build solution I can come up with to tack onto the website? If all goes wella nd we can show some proven results with Search Engine bdding/placement it is likely they will allow us to out source their Online Marketing needs to really drive home traffic (which is what I want). We've had this client for over 4 years and their products are a big hit and they can be much much bigger. We just have to show it to them that it can be. Thanks all. Sorry for wrong list but I know PHP can handle with with a MySQL backend.. Just need some ideas on how. Regards, Aaron