file download with temporary link using php
<p>I am working on a project where the user would be able to buy media files. 
after the payment is processed I would like to allow them to download the file. 
I guess it is safe to say that I should have a temporary link to the files. one that is linked to the IP of the user and perhaps a timestamp?
the problem is I dont know where to start with that.
First of all. is this the way to do it? if so..how do I proceed using php. ( i guess I dont need the exact script just hints on how to do it although if there is an existing script I would not mind) 
thank you.</p>
