Phalcon PHP is a web framework delivered as a C extension providing high performance and lower resource consumption. It is a full-stack framework. It promotes the MVC architecture and it has many features like an ORM, a Request object library, a templating engine, caching, pagination, etc.
Phalcon is really different from other php framework. Because PHP module written in C. Also, Phalcon is open-source. You have rights to modify the code and recompile it if you want.