Zend Framework is a high quality and open source framework for developing Web Applications and Web Services.
Built in the true PHP spirit, the Zend Framework delivers ease-of-use and powerful functionality. It provides solutions for building modern, robust, and secure websites.
First I have observed is it really has powerful functionality. Framework includes classes for working with databases, RSS-feeds, remote HTTP-servers, Web-forms data, JSON, mail, different Web-services (include classes for Amazon, Flickr, and Yahoo), MVC implementation, and also facilities for generating PDF-documents and logging.
This is very serious framework, but I doubt efficiency of it. I don’t want to get just another PEAR library. I will look it more precisely in the near future.
You can download it here.