accessing value of a constant from another page

[freefony]

hi am going thru a joomla script and they are accessing a constant without re-defining it or including the file where it was originally define. the first line of codes on the script is

defined('_JEXEC') or die('restricted access');
 

how is this possible

[Dormilich]

this line simply checks, whether the constant _JEXEC has been already defined or not. besides that, the line does not access the constant itself, only the name is passed.

[Markus]

The purpose of this is to prevent direct access to the file. If you access the file directly (e.g. http://your.tld/include/protected.php), the constant _JEXEC isn't defined. However, if this file is included via a PHP file where that constant has been defined, it will load appropriately.

<?php
define( '_JEXEC', 1 );
 
// access-protected file
include 'included/protected.php';