Swoole PHP is a coroutine based asynchronous network application framework. It is a PHP extension that extends PHP core and utilizes more power provided by Linux OS. Unlike the callback style single thread asynchronous I/O provided by the other networking libraries like Node.js, Swoole PHP has multiple asynchronous I/O threads and native coroutines to manage the execution of concurrent tasks. Other than asynchronous I/O and coroutine, we can also use the Linux system API and interface exposed by Swoole PHP, such as process management, system signals handling, timer and scheduler, poll and epoll I/O, memory management, etc.