Hello, can someone please fix this try it yourself editor. I have been following a tutorial and i have everything, even deleted what i wrote and copy-paste the code directly from the tutorial and it still doesn't work.

HTML Code:
<!--index.html-->
<html>
<form method="post" action="tryit-result.php" target="result">
<button>Try it</button>
<table>
    <tr>
        <td><textarea name="html"></textarea></td>
        <td><textarea name="css"></textarea></td>
    </tr>
    <tr>
        <td><textarea name="js"></textarea></td>
        <td><iframe src="tryit-result.php" name="result"></iframe></td>
    </tr>
</table>
</form>
</html>
HTML Code:
<!--tryit-result.php-->
<html>
<head>
    <style type='text/css'>
        <?php echo file_get_contents('css contents')?>
    </style>
    <script type='text/javascript'>
    $(function() {
        <?php echo file_get_contents('js contents')?>
    });
    </script>
</head>
<body>
    <?php echo file_get_contents('html contents')?>
</body>
</html>