Referencing a file in a parent directory

Question

Is this the right way to go about referencing a file in a parent directory relative to a php source file?:

require_once('../referenced_file.php');

Answer 1

To include a file relative to the current source file you should use the full path:

require_once dirname(__FILE__) . '/../referenced_file.php';

As the current working directory is set to the directory of the script that was initially executed.