The Ask About PHP blog has a tutorial offering CodeIgniter users an alternative to the "no normal GET variables allowed" restriction the framework puts on its URLs - a hack to add those GET values back in as a configuration item.
Codeigniter does allow you to turn on the querystring capability, but that would mean you have to use a pure querystring approach, foregoing the segment-based approached. So, is it possible to mix segments and querystring?
Because of how the segmenting URLs are handled, the order of the parameters is very important as they're passed directly into the controller that way. By bypassing this structure and grabbing the GET variables out of a constant in one of the configuration files in one of two ways - mixing them globally and mixing them locally.