Code generater, down load system

I want a system that can generate 50,000 alpha numeric codes, or import them from a csv file, save them in to a database. What will happen is a use will enter this code in to a input box, if it is in the database it will push a download assigned to that group of codes. SO I as admin will upload a digital file, assign upload or generate a number of codes to save against that file. User will input code on to web site - then push its download to the user or say - code not found. Paramters, set number of days codes may be valid for, Set number of downloads allowed from the code. Set number of allowed ip address to use code on. Record number of downloads in total for the download. The system may have 20 of these running at the same time, so must be able to generate the code to past for the input box on to a web site. mysql and php systems only. buget 500us.