Dont listen to the guys who waste your(and their) time responding to posts even though they admit they dont have an answer or know anything about Windows.
You can instantiate most dlls in PHP
Shopcart.dll is a dll I created in VB6 and use in PHP4
$cart = new Com("shopcart.cart1") or die("Can not start com object");
if ($cartid == "")
{
//This is how you call methods of your dll
$cartid=$cart->createCart($custid);
}
Obviously this only works in Windows