i was wondering how i can make a script that when the customer clicks the buy button for my webhosting accounts:

1. a new browser pops up and performs these functions:

2. Asks if the user needs to purchase a domain name
- if yes: go to my enom site or script and makes purchase
then goes back to the purchase form.
-if no: continues to the purchase form.

If it helps, i'm using h-sphere as my control panel. Aparently they have their own method using opensrs but i don't want to use them because i already filled my enom account with funds. Thank you in advanced for your help.

This should get you started:
<?php

switch ($action) {
case "yes":
print ""; // print out rest of order form if he clicks "yes", I have a domain.
break;
case "no":
print ""; // print's out domain order form, if he clicks no, I dont have a domain.
break;
default:
print ""; // print's out the defualt.
}

?>

Thanks for the start...i'm really new to php. can u show me how i can make it so this opens up in a new browser?

The popup would have nothing to do with PHP, it's either HTML or JavaScript. PHP is a server side language

www.javascript.com is a good starting point.