How can the use of $_SERVER['DOCUMENT_ROOT'] improve file inclusion in PHP?

When including files in PHP, using the $_SERVER['DOCUMENT_ROOT'] variable can improve the file inclusion process by providing the absolute path to the root directory of the server. This ensures that the file path is always correct regardless of the file's location within the directory structure.

<?php
include $_SERVER['DOCUMENT_ROOT'] . '/path/to/file.php';
?>