H2o is a template engine that offers an enjoyable template authoring experience for PHP. It encourages clean and readable template syntax, a compact, extensible template engine, and a very clean code base. It supports template inheritance, duck-typed variable lookup for PHP objects, a useful set of bundled tags, and filters and extensions for strings, HTML formatting, and internationalization.
Alchitect helps you build Web sites and Web applications with unprecedented ease. With Alchitect, the core things that you have to do for every Web application, especially those that require a database, are handled for you. This means you have more time to design the look-and-feel of your site as well as to add features to your application.
Kohana is a PHP 5 framework that uses the Model View Controller architectural pattern. It aims to be secure, lightweight, and easy to use. Although it reuses many common design patterns and concepts, there are some things that make Kohana stand out. It is community driven, uses strict PHP 5 OOP to provide visibility protection, automatic class loading, overloading, interfaces, abstracts, and singletons, and is extremely lightweight. Kohana has no dependencies on PECL extensions or PEAR libraries. Large, monolithic libraries are avoided in favor of optimized solutions.
Zend Framework is a framework for PHP 5 that is based on simplicity, object-oriented best practices, corporate friendly licensing, and a rigorously tested agile code base. It is focused on building more secure, reliable, and modern Web 2.0 applications and Web services, and consuming widely available APIs from leading vendors like Google, Amazon, Yahoo!, and Flickr, as well as API providers and cataloguers like StrikeIron and ProgrammableWeb.