IMHO the only two PHP frameworks you need to care about are: Symfony2 (think a PHP equivalent to Django or Rails) and Silex (think a PHP equivalent to Sinatra).
I've just spent the weekend porting an old site to Silex and Twig (a PHP equivalent to HAML) and its been a breeze.
Both frameworks come from the same people and have excellent documentation and support (i.e. they are not run by a couple of geeks somewhere who might suddenly stop developing them once they get bored). See: http://symfony.com/elevator-pitches
I've just spent the weekend porting an old site to Silex and Twig (a PHP equivalent to HAML) and its been a breeze.
Both frameworks come from the same people and have excellent documentation and support (i.e. they are not run by a couple of geeks somewhere who might suddenly stop developing them once they get bored). See: http://symfony.com/elevator-pitches