Laravel!

PHP (version 4 or 5) framework with a thin model layer. Includes an ActiveRecord class for database agnostic (mostly) data retrieval. Good community support in its forums.

Symfony is a set of reusable PHP components and a PHP framework for web projects.

Yii is a high-performance component-based PHP framework best for Web 2.0 development.Yii comes with rich features: MVC, DAO/ActiveRecord, I18N/L10N, caching, authentication and role-based access control, scaffolding, testing, etc. It can reduce your development time significantly.

Agile Toolkit is a PHP framework for developing Web User Interfaces. Inspired by desktop GUI it provides a full object-oriented foundation for Business and Presentation logic of your web software. Agile Toolkit is notable for it's simple of use and development efficiency.

Extending the art & spirit of PHP, Zend Framework is based on simplicity, object-oriented best practices, corporate friendly licensing, and a rigorously tested agile codebase. Zend Framework is focused on building more secure, reliable, and modern Web 2.0 applications & web services, and consuming widely available APIs from leading vendors like Google, Amazon, Yahoo!, Flickr, as well as API providers and cataloguers like StrikeIron and ProgrammableWeb.

FAT-FREE is a powerful yet lightweight PHP 5.3+ Web development framework designed to help you build dynamic and robust applications - fast!

Fuel is a simple, flexible, community driven PHP 5.3 web framework based on the best ideas of other frameworks with a fresh start and a design pattern in HMVC.

(Wikipedia) Phalcon is a high-performance PHP web framework based on the model–view–controller (MVC) pattern. Originally released in 2012, it is an open-source framework licensed under the terms of the BSD License.

Nette Framework is a popular tool for PHP web development. It is designed to be the most usable as possible and is definitely one of the safest one. It speaks your language and helps you to easily build better websites.

Silex - The PHP micro-framework based on Symfony2 Components

Small and carefully designed PHP 5.2+ HMVC framework.

Adianti Framework is an open source, object-oriented web application framework implemented in PHP 5 by Adianti Solutions. Adianti Framework is a component-based and event-driven framework that uses commonly known enterprise design patterns like MVC (Model View Controller), Front Controller and ORM (Object-Relational Mapping) design patterns like Active Record and Repository. Adianti Framework is also the first framework in the world that provides two different widget toolkits, one for Web applications (HTML/CSS) and another for graphical applications (with Graphical User Interface) that uses Gtk internally. »

SingularCore is a fine product powered by Zend Framework that provides instruments to create complex custom solutions where standard CMS’s won’t work or where you need too much customization in popular engines.