PHP script to sort files into folders based on file name.

I need someone to write me a simple PHP script. I have a folder with a whole bunch of files in it (named simply by number) Eg /folder1/[login to view URL] /folder1/[login to view URL] I need a php script to take each file, and reorganise them into different directories dependent on the file name divided by 1000. So it would take /folder1/4534/jpg and move it to /folder4/[login to view URL] (because 4000/1000=4) /folder1/[login to view URL] to /folder6/[login to view URL] Hopefully a quick and simple job for someone.