New Magic constants in PHP 5.3 __dir__

We know that PHP provides a magic constant (magic constant) __file__, which points to the currently executing PHP script. However, PHP does not directly provide a constant for the directory in which the script resides. That is, if we want to get the directory where the current PHP script resides, we need to use the DirName () function:

<?php
$dir =dirname(__FILE__);
?>

In PHP5.3, a new constant __dir__ is added, pointing to the directory where the currently executing PHP script resides.

For example, the currently executing PHP file is/www/website/index.php

Then __file__ equals '/www/website/index.php '

and __dir__ equals '/www/website '

Now we want to include files in the current file directory or subdirectory, which you can use directly:

<?php
require_once __DIR__ . '/path/to/test.inc.php';
?>