Need help - Content Grabber

Hello world,

I hope I made the title correct, but I need some sort of help/advise.

I have this code in my index.php to call php files to insert in the <div id=“main”>, it works fine but whenever I want to adopt some additional sample, say news system, this code is simple not compatible. Can you provide me a some sort of sample?

This is what I have got:

		<!-- main starts here -->
		<div id="main">		
		
		<?php

		if (empty($_GET['cat']) ) 
		{ $cat = 'pages'; } 
			else 
			{ $cat = ($_GET['cat']); }
				if ( empty($_GET['page']) ) 
				{ $page = 'home'; } 
					else 
					{ $page = preg_replace('/[^a-zA-Z0-9]/', '', $_GET['page']); }
						if ( file_exists($cat . '/' . $page . '.php') ) 
						{ include ($cat . '/' . $page . '.php'); }
							else
							{ include ('pages/error.inc.php'); }
		?>
		<!-- main ends here -->								
		</div>				

This is where it came from:

INDEX.PHP

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">

<head>

<meta ............ />

<link rel="stylesheet" ................ />
<?php include('counter.php'); ?>
<?php include('variables.php'); ?>

<title><?php echo $title ?></title>

</head>

<body>

<!-- wrap starts here -->
<div id="wrap">

<?php include('header.php'); ?>
<?php include('menu.php'); ?>			

	<!-- content-wrap starts here -->
	<div id="content-wrap"><div id="content">				
		
		<!-- sidebar starts here -->
<?php include('sidebar.php'); ?>
	
		<!-- main starts here -->
		<div id="main">		
		
		<?php

		if (empty($_GET['cat']) ) 
		{ $cat = 'pages'; } 
			else 
			{ $cat = ($_GET['cat']); }
				if ( empty($_GET['page']) ) 
				{ $page = 'home'; } 
					else 
					{ $page = preg_replace('/[^a-zA-Z0-9]/', '', $_GET['page']); }
						if ( file_exists($cat . '/' . $page . '.php') ) 
						{ include ($cat . '/' . $page . '.php'); }
							else
							{ include ('pages/error.inc.php'); }
		?>
		<!-- main ends here -->								
		</div>				
				
	<!-- content-wrap ends here -->		
	</div></div>

<?php include('footer.php'); ?>
	
<!-- wrap ends here -->
</div>

</body>
</html>

Thanks in advance.

Regards,

Bong