Phalcon is an open source, full stack framework for PHP 5 written as a C-extension providing high performance. You don't have to learn or use C language, functionality are exposed as PHP classes you can use any time. Phalcon is also loose coupled thus you can select specific parts of the framework for your development.
Benchmarking below shows how efficient Phalcon is when compared with other traditional PHP frameworks. This benchmark is updated as stable versions are released from any of the frameworks mentioned or Phalcon itself.