CodingForums.com - PHP frame/includes problem

Hi! I'm new to PHP, so forgive me if I am missing an obvious answer. I can't get a small portion of my include or switch statement to work correctly.
I am trying to develop my own site using PHP instead of frames with this layout:

|_________________________|
|_______ Header __________|
|_________________________|
[__ Nav1___ Nav2 ___ Nav3 __]
|_________________________ |
|_________________________ |
|_________________________ |
|_______ Content __________|
|_________________________ |
|_________________________ |

But within the content, I am trying to make a seperate navigation list like this:

(Content)
| [subnav item1] ___ subContent _____|
| [subnav item2] ___________________|
| [subnav item3] ___________________|

where the subContent changes depending on which subnav item is clicked.

To do this, I've been using something like this:

Code:

<!-- Sample -->

<div id="header">

       <?php include('header.php')?>

</div>



<a id="nav" href="index.php?page=nav1">Nav1</a>

<a id="nav" href="index.php?page=nav2">Nav2</>

//etc for nav3



<?php

       $page = $_GET['page'];



       switch ($page){

                 case "nav1":

                        include('Nav1.php');

                       break;

                //etc for nav2, nav3

                 default:

                        include('home.php');

         } ?>



And then within Nav1 I will have:

           <div id="subnav">

                  <?php include('subnav.php')?>

            </div>



            <div id="subcontent">

                   <?php 

                        $subc = $_GET['page']

                       switch($subc){

                                  case "sn1":

                                      include('subnav1.php'); break;

                                  default: include(Nav1_home.php) }?>

etc..

So when I visit my page, everything works except the includes statement for the content. The address bar would say "http://website.com/index.php?page=subnav1" but it would show the home page instead of the content which was written in the file subnav1.php. But however, when I visit say Nav1, the default includes "Nav1_home.php" will show up in the subcontent area

Is this because I can't do multiple switch/include statements within each other? How can I work around that? If not, what am I doing wrong?

I've been trying to search multiple forums for a problem close to this but I have not been able to come across one :[