a way to download file after purchase?

How are they going to pay? If you are planing to use PayPal then implement the API from then.
There you could set the return url. Make sure you verify the information before let them download.

Thanks for the quick reply and yes they will be paying with PayPal.

Can you explain to me a little more what it is you mean exactly please?

https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/howto_api_reference

so after i implement the api i should set up a private page where they can gain access to download the files? Would that work?

I would say after the successful payment the API will post the details to the link you point. Direct the other page from there and make sure to verify the referrer from PHP. so that any one trying to access it directly will not gain access.

ok. i think i understand what you’re saying so I will give it a shot.

thanks for your help!