Loading PHP pages in one PHP file

Hi
I'm New in PHP and want to create a smoll web site in HTML include some PHP Code.

So here is my problem :
i want to know how can i load PHP pages i've previesly created in one PHP file. For exemple, i have this menu : (home l about l service l contact)
and i've created the page corresponding each title in that menu (home.php, about.php, service.php and contact.php).
however i've an index.php file that include the header and the footer.

So, now i want to know what can i do in order to load the other pages in the middle of my index.php file, when i click in a title in the menu ?
and also the most important thing is how shall i code the links in the menu to load each corresponding page in the index.php file ?

one last thing : i've been suggested to use the Switch/case statement.
here is an exemple :

<?php
if ( isset ( $_GET ['page'] ) )
{
switch($_GET ['page'])
{
case "about":
include("about.php");
break;
case "Service":
include("Service.php");
break;
case "Contact":
include("contact.php");
break;
}
}
else
{
include ("home.php");
}
?>

But the problem is that i neither know how to use it nor how to define the links where we should click and let this Switch statement work.
So i want to know what can i do so when i click in the title in the menu the corresponding page will be loaded.
(Sure i'm not good in PHP, but i can manage. That what i use to do)

even Just a smoll replay will be apreciate.

Thank you very much for every one