Not a good idea to use GET, with get hackers or even anyone could use the passthru command to upload and file to your server, they could also view your servers password file which will include your username and password needed to login to your cpanel(or whatever your webhost uses). I reccomend using $_REQUEST['target'] and putting the following code into a file like grabpage.php then including grabpage.php(or whatever you called it) on the index page where you want the content to show up
<?php
$page = $_REQUEST['page'];
if(eregi("[a-z0-9\-_\.]+", $page, $regs)) //make sure $page is alphanumeric
{
$dir = "includes/"; //not strictly necessary, can be blank.
$ext = ".php"; //.php, .html, .txt, whatever
if(file_exists($dir . $page . $ext))
{
include($dir . $page . $ext); //or readfile if not expecting php code
}
else
echo '404 - Not Found'; //or something similar
}
else
echo 'Not a recognized page.';
?>