The framework must have little learning and easy to expand. I am using http://sourceforge.net/projects/naanalframework/ for all my projects. There is no installation. Just has to point the frameworks naanal.php in your application's index.php and run it. The framework will guide you what to do. For the beginer, this framework is very useful to develope PHP applications. A sample application also available at http://sourceforge.net/projects/naanalframework/files/sample%20applications/wordpress_plugin_builder.zip/download
I really like Kohana, but if you're going for big corporate projects, you might want to consider the Zend Framework. Once you know one good MVC framework (and the underlying OOP logic), though, you can fairly easily learn more.
There are lots of Frameworks available to learn. As per my experience, i would like to suggest you Yii, CodeIgniter, Zend as they have lots of flexibility, features as well as MVC concept.
It depends on personal requirements and market demand also vary location to location.Moreover you should read this article for better answer. http://iwebeffects.com/what-is-php-framework-how-it-works-and-which-one-you-should-use/
What can I say: - Zend - very heavy and functionality overloaded framework - Yii - great framework, but not transparent (not for newbies) - Kohana - great framework which I'm using now I met also other frameworks but didn't work with them much.
if you choose symphony 2, you'll get the advantages of learning Drupal as well coz Drupal 8 will implement some of symphony 2 modules.
Start with CodeIgniter. It is very easy to learn. Then learn Yii-Framework. This will make you very fast. I learnet both and I can say that Yii is much better than CodeIgniter.