@jakzal the require_once fails if you have a library installed globally or in a phar using this component and this library calls your php code using the local version, as it would not be the same file. Imagine the Debug component is used in Behat or PhpUnit for instance.

@ShiraNai7 please use ``'/'`` instead of ``DIRECTORY_SEPARATOR``. It works cross-platform to require file as of 5.3 and it is more readable