อยากแนะนำแบบมีreference ทำไง คำสั่งแบบนี้ /?ref=name ใช้งานอย่างไร

<!-- Container -->
<? 
switch ($_GET["page"]) {
case "home":
	include("page_home.php");
	break;
case "service":
	include("page_service.php");
	break;
case "product":
	include("page_product.php");
	break;
case "aboutus":
	include("page_aboutus.php");
	break;
case "contactus":
	include("page_contactus.php");
	break;
default:
	include("page_home.php");
}
?>