Errors with require_once in php <p>I don't know why when i add a require_once function in my code, it can not run, always show that failed to open stream.</p> <pre><code>&lt;?php require_once("../../../../cadpro_vs2/include/admin/ad_nav.php") ?&gt; </code></pre> <p>Any mistake on syntax or something, please help!</p> <p>Can anyone help me?</p>