If you're going to have a lot of users and files, I would recommend create a folder for each user and then store each uploaded file within there. Rename each file, too, using the ID from the database. So you have a 'users' table and a "files" table. The files table would reflect the user ID along with the other data. Then a file might be stored as x/y, where "x" is the user ID and "y" is the file ID.