Hi can anyone tell me how i can achive this.
I have a product to sell online and will use alertpay but i have some additional information i want the user to fill in before they press the buy button to take the to the payment area.user must give the detail name,address,email etc..and i want when they press buy the form is submit to my email and after the payment take them to the Product page..

can someone help out please

Hello mousumisrety (quite a name u got dere :-) ),

I assume you've already created the form for the website you're talking about. It's pretty easy from there.
First, you add a few validations to the database fields (e.g NOT NULL) so that the user is forced to enter a value. This also has to be implemented in the front end so the user does not see some weird error message and get confused. Regular expressions also go well here too (google for regular expressions if you dont have an idea about it).
This link introduces you to the php mail() function. There aer other materials online too, so dont limit yourself to that.

And finally, post a sample of what you've done so far, the errors you're getting and you'll receive a lot more help.