amphp : Amp is a non-blocking concurrency framework for PHP providing primitives to manage concurrency such as an event loop, promises, and asynchronous itera...
Fat-Free Framework : A powerful yet easy-to-use PHP micro-framework designed to help you build dynamic and robust Web applications - fast!
WikkaWiki : WikkaWiki is a flexible, standards-compliant and lightweight wiki engine written in PHP, which uses MySQL to store pages.
Elgg : Elgg is an award-winning social networking engine, delivering the building blocks that enable businesses, schools, universities and associations to cr...
Symfony is a set of reusable PHP components and a PHP framework for web projects.