ReactPHP
Event-driven, non-blocking I/O with PHP
... event-driven architecture makes it a perfect fit for efficient network servers and clients handling hundreds or thousands of concurrent connections, long-running applications and many other forms of cooperative multitasking with non-blocking I/O operations. What makes ReactPHP special is its vivid ecosystem with hundreds of third-party libraries allowing you to integrate with many existing systems, such as common network services, database systems and other third-party APIs.