E-Commerce Web Tracking Script

Hi, we need a web tracking script to track some e-commerce events. The point is that we want to analyse which comparision shopping sites and products perform well. For this purpose users getting redirected from comparison shopping sites to our shops with http parameters like ( [login to view URL]). What we need now is a Javascript to track the client site, set cookies and so on. On every order placed, the javascript should send the order and if available the information about the conversion (feed,product,client) to a server side php script. This php script is also part of the project. The php script should contain an order class and a basic processing getting the order parameters. Database processing will be made by us. The solution should be able to work in an cross domain environment. A short readme documentation should be included how (sample code) we integrate this script into our product details and order confirmation pages. Http parameter which should be tracked are: client feed product Variables we need for every order: OrderID TotalAmount SubTotalAmount (optional) TaxAmount (optional) ShippingAmount (optional) Variables we need for every order line: SKU Title (optional) Group (Array / optional) Price Qty Please ask me if you have further questions or perhaps other ideas.