There are many blogs on this topic detailing the pros and cons of each framework, which at the end still leaves you clueless.

I understand that having to learn a new PHP MVC framework takes a lot of time and energy and one need to be absolutely sure about the framework you adopt, you've heard about Codeigniter, CakePHP, Symfony, Yii etc. which one to choose!

Zend Framework evaluation key facts

  1. Who's behind the framework: Zend Framework is backed and endorsed by The Zend Company, IBM and other strategic partners. This is absolutely vital for the longevity of the framework and related technologies, (remember what happened to Codeigniter)
  2. Enterprise quality: The code base is of highest quality, fully standardized and professional OOP practices are emphasized, unlike many other frameworks which are aimed at entry-level developers, RAD and bad coding practices.
  3. Use at will: ZF is a glue framework, meaning you can use some or all of the components to model your application.
    ZF does not make any assumptions about your application and is flexible enough to cater for virtually any use case. You will find an arsenal of professional, production-ready libraries all built by the Zend Company for ZF to simplify development, unlike a variety of ad-hoc, buggy 3rd party plugins etc. you'll find in some other frameworks.
  4. Documentation & support: The Zend Framework documentation, bug track and tutorials these days are pretty good and the ZF community has also grown rapidly over the last few years. There is also an IRC channel for live support.
  5. Opportunities: Looking for a job as a professional PHP Developer?, you will find that the many companies are serious about Zend, not just the framework, but related technologies and Zend Certification as well