Prevent that anybody can open include file directly in his browser

I have a file named startpage.inc.php and I want to include it but prevent, that anybody can open it in his Browser. Is it possible?

Possible:

<?php
include 'inc/startpage.inc.php';
?>

To prevent:

www.example.org/inc/startpage.inc.php

You have several options.

• Check whether a constant is defined within your file. If not, exit;. Define a constant in the file that includes your startpage.inc.php. This is how a lot of free scripts prevented unwanted inclusions.

• Don't have the script in the publicly available folder. Move it below document root so it can never be accessed directly, only when included via include or require.