PHP Program modification for website

I have a PHP auction management software which will allow me to have my own auction site. The business will be in books where users can trade on this platform. For our site though, we want users to sell a specific product for a fixed priced similar to [login to view URL], alibris and amazon site model. Basically having a complete user driven site. 1. A search based shopping cart of member's current products. The search returns from a database a relevant listing of items for sale. Clicking on a particular listing brings up the member(s) who are selling this product. The shopping cart database must be integrated with item #2. 2. Members must be able to post/edit/delete items from the database associated with the shopping cart. 3. Ability to track all sales during the month then invoice members (preferably automatically). I guess in general I'm looking for a shopping cart system that set's the administrator up as a service medium. That is, I'm not selling my products, rather my product is allowing others to sell their's through my site. If the modifications is something you think that can't be done then can this be created from scratch or please give me suggestions or information that can lead me to acquire something like this. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform - Linux - PHP - html - SQL