Swoole — Coroutine-Based Async PHP Runtime

Introduction

Swoole extends PHP with an event-driven, coroutine-based concurrency model. It allows PHP developers to build high-performance TCP/UDP/HTTP/WebSocket servers without switching languages.

What Swoole Does

• Adds native coroutine support to PHP for concurrent I/O
• Provides built-in HTTP, WebSocket, and TCP/UDP servers
• Implements async MySQL, PostgreSQL, and Redis clients
• Offers process management and task worker pools
• Supports millisecond-precision timers and signal handling

Architecture Overview

Swoole is a C extension for PHP that runs as a persistent process (not per-request like PHP-FPM). It uses an event loop powered by epoll/kqueue at its core, with a multi-process reactor model. Coroutines are stackful and scheduled cooperatively, yielding automatically on I/O operations so other coroutines can proceed.

Self-Hosting & Configuration

• Install via PECL (pecl install swoole) or compile from source
• Enable the extension in php.ini with extension=swoole.so
• Configure worker count via $server->set(['worker_num' => 4])
• Use Docker image phpswoole/swoole for containerized deployments
• Set swoole.use_shortname to control function alias behavior

Key Features

• Stackful coroutines with automatic yield on I/O
• Built-in connection pooling for databases and Redis
• HTTP/2 and WebSocket server support out of the box
• Shared memory tables for inter-process data sharing
• Process and task worker management with message passing

Comparison with Similar Tools

• ReactPHP — event-loop async without coroutines; Swoole uses coroutines for synchronous-style code
• Workerman — pure PHP async server; Swoole is a C extension with higher raw throughput
• RoadRunner — Go-based PHP app server; Swoole runs entirely within PHP process space
• FrankenPHP — embedded PHP in Caddy; Swoole provides its own server and async primitives
• Node.js — similar event-driven model but Swoole lets teams keep their PHP codebase

FAQ

Q: Does Swoole work with Laravel? A: Yes. Laravel Octane provides a first-party Swoole adapter for persistent application serving.

Q: Can I use existing PHP libraries with Swoole? A: Most libraries work, but blocking I/O calls should be replaced with Swoole coroutine-aware clients for best performance.

Q: Is Swoole production-ready? A: Yes. It has been used in production by companies handling millions of concurrent connections since its initial release in 2012.

Q: What PHP versions does Swoole support? A: Swoole supports PHP 8.1 and above for the latest releases.

Sources

• https://github.com/swoole/swoole-src
• https://www.swoole.co.uk/docs