CodeIgniter

http://www.thecredence.com/php-frameworks-which-one-is-most-suitable-for-you/
http://www.avnetlabs.com/php/php-framework-comparison-benchmarks
http://www.phpframeworks.com/
http://www.phpit.net/article/ten-different-php-frameworks/

http://www.devtrench.com/codeigniter-vs-symfony/
http://www.usenet-forums.com/php-general/53912-symfony-vs-cakephp-vs-code-igniter.html