PHP Coder to make small change to existing PHP App

We want the PHP coder to modify part of an existing simple app. We HAVE an existing PHP that allows the user to select a category (a subcategory), subcategory (auto populates based on category selected), and year (auto populated based on subcategory selected). When submitted user sees a list of links that when clicked open up an attachment. There is an admin area for the user to add/manage categories, subcategories, and attachments We want to modify this slightly so user will select Category which will then populate a drop down of years (only years with attachments will show). When the year is selected it will autopulate the list of months (January to December) that have data. User then selects month and clicks on submit with will then show the list of links. So the developer will need to modify the front end, DB, and backend in order to achieve this. Also, we want to allow either attachments OR urls. This hierarchy is much more simjpler than the previous app so deletion of some fields will be likely.