Skip to content
Analysis
Swoole

Swoole / OpenSwoole

  • Language: C/C++ (PHP extension)
  • Architecture: PHP extension that transforms PHP into an async, event-driven, coroutine-based runtime. PHP IS the server — no Go layer.
  • Creator: Swoole (original), OpenSwoole (community fork after license change)
  • Maturity: High but complex. OpenSwoole 26.2.0 (Feb 2026) added PHP 8.5 support, native Fiber coroutines, io_uring reactor.
  • License: Apache 2.0

How It Works

  • Installed via PECL (pecl install swoole), not Composer. Extends the PHP CLI runtime.
  • PHP code directly creates HTTP/WebSocket/gRPC servers using async APIs.
  • Coroutines allow synchronous-looking async code.
  • SWOOLE_HOOK_ALL intercepts blocking PHP functions (PDO, curl, file I/O) and makes them non-blocking automatically.

Features

  • HTTP, WebSocket, gRPC servers created directly in PHP
  • PDOPool, RedisPool, generic ConnectionPool — first-class database connection pooling
  • Swoole\Table — shared-memory hash table (>2M ops/sec), in-process Redis-like store
  • OpenMetrics/Prometheus output (OpenSwoole 4.9+)
  • Coroutine-hooked stdlib (PDO, cURL, Redis become async transparently)
  • Multi-process mode, task workers, process pools

Does NOT Have

  • Automatic TLS / Let’s Encrypt
  • Multi-node clustering
  • Debug/profiling UI (Xdebug step debugging added in OpenSwoole 26.2.0)
  • Query analysis tools
  • Cross-platform support (Linux-only in practice)

PHP-Side Requirements

  • Most invasive. Entire entry point rewritten.
  • Superglobals ($_GET, $_POST) do NOT work — must use $request->get, $request->post
  • echo does not work — must use $response->end()
  • session_start() does not work
  • Static/global variables shared across concurrent coroutines — data leak risk
  • Must use Coroutine::getContext() for per-request state isolation
  • Not Composer-based (PECL C extension)

Server example:

$server = new Swoole\Http\Server('0.0.0.0', 9501);
$server->set(['worker_num' => 4, 'hook_flags' => SWOOLE_HOOK_ALL]);

$server->on('Request', function($req, $res) {
    // $req->get instead of $_GET
    // $res->end() instead of echo
    $res->end('Hello ' . ($req->get['name'] ?? 'world'));
});

$server->start();
Roadrunner