City, State radius search

I am in need of a simple, well documented script written in PHP that does the following: Someone types in either a zip code or a City, State and a radius and it returns all the results that meet that criteria. This is for the US only. I will also need the database with all the information required for this script to run. Before the transaction completion I would like to see a demo of the search tool with some sample data. =================== They data they will be getting is via user submissions. For example, a user can go to the submission page, fill in fields such as an Item Title and then an Item Subject. They would then specify the zip code, city and state this item is located. I have that portion completed. Now I need the ability to search by either zip code or a combo of City and State.