Zend Framework
Zend Framework is an object oriented framework written in PHP 5. It is based on simplicity, corporate friendly license, and a rigorously tested agile codebase. The loosely coupled architecture also allow developers to use Zend components within other framework.
Symfony
Symfony is a PHP 5 framework which provides an architecture, components and tools for developers to build complex web applications faster. The official site provides a practical tutorial for Symfony beginner too.
CodeIgniter
CodeIgniter is another popular PHP framework. It has the advantage of having a wiki for easier navigation. New users can get started easily by referring to its documentation. It supports PHP4, which makes it canft take full advantage of PHP5.
CakePHP
Using commonly known design patterns like MVC and ORM within the convention over configuration paradigm, CakePHP reduces development costs and helps developers write less code.
Prado
Prado require PHP5 and above to run, and it is a component-based and event-driven programming framework for developing Web applications. There is a quick start tutorial for beginner too.
Yii
Yii is a high-performance component-based PHP framework best for developing large-scale Web applications. It has a full stack of features and written in strict OOP(require PHP5 and above).
Akelos
The Akelos PHP Framework is a web application development platform based on the MVC (Model View Controller) design pattern.