swoole/swoole-src

Swoole is a performance extension for PHP that gives the language capabilities it doesn't have out of the box: event-driven, asynchronous, and coroutine-based concurrency. In plain terms, it lets a single PHP application handle thousands of simultaneous connections without freezing up or waiting idle while one task finishes before starting the next. By default, PHP handles one request at a time per process, which is slow for high-traffic sites. Swoole changes this by running an in-memory server (rather than through traditional web servers like Apache) and automatically converting ordinary PHP blocking operations, database queries, HTTP calls, file reads, into non-blocking ones. This happens transparently: you write code that looks like normal sequential PHP, but under the hood Swoole switches between lightweight threads called coroutines so no time is wasted waiting. It also supports WebSockets, HTTP/2, TCP, and mixed server setups. You would use Swoole when building a PHP application that needs real-time features (like a chat app or live dashboard), high throughput (like a payment API under heavy load), or simply wants much faster response times than a traditional PHP setup. The library is written in C++ and installed as a PHP extension, and it can be run quickly via Docker.