PHP Relative Indexing

If I have two PHP files, and one includes another, and the one that’s included calls something via relative addressing, is it relative to the file that calls it or to the actual file being included?

Example:

loader.php:
#include("…/…/…/included.php");

included.php:
$myDirectory = opendir(".");

What directory has been opened? The one that loader.php is in or the one that included.php is in?