Ajax php fallback

ajax-fallback.php

<?php
                    ob_start();
                    chdir("./content");
                    $file = "./".$_GET["page"].".php";

                    if(!file_exists($file))
                    {
                        $file = "./404.php";
                    }
                    include($file);
                    chdir("..");
                    $content = explode("----------", ob_get_clean());
                ?>
                <div id="title_menu">
                    <? echo $content[0]; ?>
                </div>
                <div id="content">
                    <? echo $content[1]; ?>
                </div>