Kohana is an open-source web application framework for PHP 5. It uses the Model View Controller design pattern and aims to be secure, lightweight, and easy to use. It uses strict PHP 5 OOP and originally based on CodeIgniter.
Kohana framework features are fast, flexible, incredible well documented and lightweight and extensible.
Kohana2 is the current stable release of the framework, which is suited for a production environment and you can download it here.