Someone

<?php
	// Assign the requested page to a shorter variable for simplicity.
	// The value of $_GET["page"] will be obtained from index.php?page=RIGHT_HERE
	$p = $_GET["page"];
	// Check for bad requests.  This is a security measure.
	if (strpos($p,"..")) {
    		// A bad request has been made, exit immediately. Do not proceed with the inclusion.
    		die("Bad page request");
 	 }
	// File to include. If $p is empty, fall back to
	// main.php. THIS FILE MUST EXIST.
	$p = trim($p); // trim whitespace
	if (empty($p)) $p = "main.php";
	else {
	  $p .= '.php';
  	if (!file_exists($p)) $p = '404.php';
	}
	$content_file=$p;
	
	
	// Set styles
	$s = $_GET["style"]; // Get style variable 
	if (strpos($s,"..")) { die ("Bad page request"); } // Security measure 
	$s = trim($s); // trim whitespace
	
	
	if (empty($s)) $s = "default.css"; // If empty then default to default.css
	else {
	  $s .= '.css';
  	if (!file_exists($s)) $s = 'print.css'; // if style file does not exist set style to print.css 
	}
	$style=$s;			
?> 




<!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 http-equiv="Content-type" content="application/xhtml+xml ;" />
    		<meta http-equiv="Content-Language" content="en-us" />
		<link <?php echo "href=\"$style\"" ?>  type="text/css" rel="stylesheet" />
		<title><?=$title ?></title>
		</head>
		<body>
		<div id="pageholder">
			<div id="header"><?php include("header.php"); ?></div>
			<div id="menu_container"><?php include("menu.php"); ?></div>
			<div id="content_container"><div id="content_container_body"><?php include($content_file); ?></div></div>
			<div id="footer"><?php include("footer.php"); ?></div>
		</div>
		</body>
</html>