Its a bit hitched from the Zend Framework.
Its not specific to any particular framework or server. (I suppose you would have to have apache and use virtualhosting)
Whats really cool about this system, is you can chain settings. EG:
setting_1 = x
setting_2 = y
setting_3 = z
Developer : Developer_1
setting_3 = a
setting_4 = i
So setting something like, APPLICATION_ENV = Developer_1, you can then chain settings and use inheritance. Like css I suppose. Of course, you have to write the logic for all that.
Its also worth taking a look at how big frameworks etc handle their settings. I really like the zend framework approach, which is why I hacked off its setting system.