Laravel - A PHP Framework For Web Artisans
Leaf - Leaf PHP is a micro-framework that allows you to create clean, simple but powerful web applications and APIs quickly..
CodeIgniter - A Fully Baked PHP Framework
Slim Framework - Slim is a PHP micro framework that helps you quickly write simple yet powerful web applications and APIs.
Phalcon - Web framework delivered as a C-extension for PHP
Flight Web Framework - An event-driven web framework, from Twitter