PHP Framework

Zend Framework
http://framework.zend.com/

CakePHP
http://www.cakephp.org/

php.MVC
http://www.phpmvc.net/

CodeIgniter
http://codeigniter.com/

Stratos Framework
http://www.stratosframework.com/

Akelos Framework
http://www.akelos.org/

Qcodo Framework
http://qcodo.com/

Prado Framework
http://www.pradosoft.com/

evoCore
http://evocore.net/

Solar PHP
http://solarphp.com/

Picora Framework
http://livepipe.net/projects/picora/

Jelix
http://jelix.org/