The goal of this tutorial is to show you how to build an AJAX powered shopping cart. However, it will not be production ready. The back end requirements vary from site to site far too much to write an effective tutorial. Instead, we are going to focus on the AJAX parts. The back end code in this tutorial acts as scaffolding for us to build the AJAX functionality, however, it can be built off of to meet your own site’s requirements. In the last section, we’ll discuss some possible next steps to implementing this in your own websites.
Link: NetTuts