Add features to a cart for me

I would like to add feature to my already built cart. The cart will include a option for seller to add products, I already made the template(form) and the database, I just need help with PhP and mysql to connect it and such. I also need an easy page that display an invoice at then end. This is about 75% of the work, I will discuss more once I pick the winner. I need it done in 2 days, I will not pay you if you can't do it in 2 days. Under 100$, This tasks should be easy if your an expert programmer in this type of work.