ขอคำแนะนำ PHP กับ CSS layout กับการ redirect page ต่างๆ

function changepage(id) {
        var element = document.getElementById(id);
        
        if(element.id === "page") {
            $("#section").load("page.php");
        } 
    }

$page = (isset($_GET["page"])) ? $_GET["page"] : "";
switch ($page) {
                    case "page":
                        include("page.php");
                        unset($_GET["page"]);
                        break;
                   
                    default:
                        include("homepage.php");
                        unset($_GET["page"]);
                        break;
                }

window.location.href="homepage.php?page=" + page;