i prefer CodeIgniter, myself, when doing PHP development. i like it because it doesn't force you into anything, but if you want to use its helpful features, you can.
Also examine Kohana - originally an offshoot of CodeIgniter, the 3.1 branch is an entirely different animal.
Kohana is more of a "toolkit" kind of framework, where most of the components only rely on a few base classes, but are otherwise surprisingly decoupled.
Kohana is more of a "toolkit" kind of framework, where most of the components only rely on a few base classes, but are otherwise surprisingly decoupled.