Ive been trying to make this happen and I think mod_rewrite might be able to do this, but I'm not sure how to dynamically change all .php requests. Nor do I know if this is a good idea.

Basically it would be really tedius to make rules for every single page, every time I add a controller.

Open
<pagename>.php

But it really loads
system/application/controllers/<pagename>.php

Yet stays on the <pagename>.php url

I don't know if this works
%{REQUEST_FILENAME}