The world of PHP frameworks is in a somewhat weird state right now with the introduction of PHP 5.3. The new features in PHP 5.3 seem to speak mostly to framework development (namespaces, late static binding, anonymous functions, __invoke() magic method).
It seems like all of the major frameworks are working on something based on PHP 5.3, but there isn't a whole lot out there yet. When these new versions (or entirely new frameworks) come out, though, they'll have some pretty radical differences.
No matter what framework you pursue for your immediate development needs, I'd pay careful attention to the development of the new stuff that's on the horizon. One framework I've been giving close attention to is the Lithium framework, written by some very talented developers, a few of which from the CakePHP project. It showcases a lot of what's possible in PHP 5.3.
http://lithify.me/
Another project to check out is the new version of Symfony (still a preview release):
http://symfony-reloaded.org/
For someone new to PHP, I'd hate for you to just barely get comfortable with the older code out there and have all of this new stuff hit you and throw you off. So, even if you don't find a 5.3-based framework that fits your needs, keeping up with the newer stuff will be worth your while.