We have a music site and we want to add a downloadable section.
Users must sign up into a database of members. Members must then pay a fee (e.g. 10 euros) directly into paypal. Once they pay this fee they can download up to five tracks from the list uploaded to a server directory. once they have downloaded five tracks they must pay the fee again to download another five tracks. they can download any number of tracks say 2 tracks, then a week later they can download more. so we need to remember the users and what files they have downloaded etc.
each specific file download must be uniquely generated and time limited.