when to use DIRECTORY_SEPARATOR in PHP code?

Question

Look at the PHP code:

require_once dirname(__FILE__).DIRECTORY_SEPARATOR . './../../../wp-config.php';
require_once dirname(__FILE__).DIRECTORY_SEPARATOR.'inc/options.php';

The above code is from a plugin from the Wordpress.

I don't understand why half of it uses DIRECTORY_SEPARATOR, but the other half uses "/" ?

Answer 1

Because in different OS there is different directory separator. In Windows it's in Linux it's /. DIRECTORY_SEPARATOR is constant with that OS directory separator. Use it every time in paths.

In you code snippet we clearly see bad practice code. If framework/cms are widely used it doesn't mean that it's using best practice code.