"Swoole is a coroutine-based asynchronous PHP programming framework."

"Swoole is a complete PHP async solution that has built-in support for async programming via fibers/coroutines, a range of multi-threaded I/O modules (HTTP Server, WebSockets, TaskWorkers, Process Pools) and support for popular PHP clients like PDO for MySQL, Redis and CURL."

TLDR: Async PHP framework