[eluser]Darrarski[/eluser]
Thanks a lot. This is very useful if we want to have several configuration environments (for example several database configs). I figured out, that is better to use require() than require_once() function in "core" config files sometimes. That's probaily because of Load class could include the config file more than once in some cases. I had a problem using tank_auth library with require_once() function in config/tank_auth.php file. With require() there is no problem at all. Thanks again for solution that doesn't require modification in CI system files.