Symfony is a great PHP5 framework for web applications. After Ruby on Rails shook the web developers, a lot of web frameworks with AJAX support started appearing. There are a few in PHP as well.
The feature list says:
* simple templating and helpers
* cache management
* smart URLs
* scaffolding
* multilinguism and I18N support
* object model and MVC separation
* Ajax support
* enterprise ready
The Symfony project website is also a place where they documented the development of Askeet – a full blown live web app done in 24 days with Symfony.
If you are a PHP developer, try it out!