what skills do you have and have you googled this?
I only ask because when I did I found an entire free script that not only let me upload a file, in this case a picture, but resize it and rename it. the resizing being the bit I didn;t know how to do
some extra bits of php and I was away
I suspect on a forum like this you have to make some of the running and not just hold your hand out expecting a fully working script to be delivered
that's the link I used, it's php and gives you the code to upload a file, you don;t need to resize, I'm a simpleton with php but managed to get it upload three files from a form and rename them and put them to a folder on the server, I'm sure there's more specific bits of code out there if you look