Build a Website

I currently have a website that a user can sign into using their [login to view URL] account. I need the code that I can insert into my website's code that will get a list of the user's inventory items, that can be filtered for specific games, and items. I also need code I can run that will get me a list of all items on the steam marketplace for certain games (Counter-Strike : Global Offensive, Dota 2, Steam, Team Fortress 2), and add that list of items into a MySQL database.