Спасибо Soniks. Получилось.
<?php

if ( !defined('MODULE_FILE') )
{
die("You can't access this file directly...");
}

$index = 1;
@require_once("mainfile.php");
@include("header.php");
?>
Ваш текст
<?php
?>
<a href="http://phpnuke.org"><img src="images/powered/powered5.jpg" border="0" alt="Powered by PHP-Nuke" title="Powered by PHP-Nuke" width="88" height="31"></a>
<br><br>
<?php
@include("footer.php");

?>