Which PHP framework?

A developer has to contend with a multitude of options when choosing a PHP framework to develop web applications. There are many excellent open source PHP frameworks that are currently being actively developed, such as:

• CakePHP
• Zend Framework
• Symphony Project
• Prado Framework
• and many others!

Many of the frameworks were modeled after Ruby on Rails, and others (actually only one so far) such as Prado is based on the ASP.NET framework. I haven't had the time to look at all of them in detail but personally, I prefer the OO and event-based architecture of Prado (given that I've done a lot of .NET stuff). In fact, I intend to take a serious look at Prado for my future projects.
This page presents a rather detailed overview of some of the popular frameworks.