Event-driven programming presents a unique challenge for PHP developers accustomed to procedural coding. In PHP's procedural nature, events often boil down to simple function calls, with no inherent asynchronous behavior. All code execution remains blocking.

However, languages like JavaScript demonstrate the potential of event loops as a central component. This insight has led developers to integrate event loops and asynchronous capabilities into PHP HTTP servers. This article demonstrates building a high-performance PHP HTTP server leveraging the Icicle library, and integrating it with Apache for optimized static file serving. The example code is available at https://github.com/sitepoint-editors/icicle-http-server.

Key Advantages

• Icicle's Asynchronous Power: Icicle's asynchronous programming capabilities enable the creation of a remarkably fast PHP server. Concurrent request handling significantly boosts performance.
• Apache Integration for Static Files: Efficiently offloads static file serving to Apache, leaving the PHP Icicle server to handle dynamic requests.
• Routing and Templating Enhancements: Extending the basic server with a router (like League\Route) allows for sophisticated request handling and routing. A template engine (such as League\Plates) adds features like layouts and template inheritance for complex applications.

Apache Configuration for Optimized Static File Serving

To avoid unnecessary PHP processing for static files, configure Apache to serve them directly:

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*) http://%{SERVER_NAME}:9001%{REQUEST_URI} [P]

This mod_rewrite configuration directs Apache to forward requests for non-existent files to a different port (e.g., 9001), where the PHP Icicle server will handle them.

A Basic Icicle HTTP Server

Begin by installing Icicle:

composer require icicleio/http

A simple Icicle HTTP server example:

// server.php
require __DIR__ . "/vendor/autoload.php";

use Icicle\Http\Message\RequestInterface;
use Icicle\Http\Message\Response;
use Icicle\Http\Server\Server;
use Icicle\Loop;
use Icicle\Socket\Client\ClientInterface;

$server = new Server(function (RequestInterface $request, ClientInterface $client) {
    $response = (new Response(200))->withHeader("Content-Type", "text/plain");
    yield $response->getBody()->end("hello world");
    yield $response;
});

$server->listen(9001);
Loop\run();

Advanced Routing with League\Route

For more robust routing, integrate League\Route:

composer require league/route

Enhanced server.php with routing:

// server.php
// ... (previous imports) ...
use League\Route\Http\Exception\MethodNotAllowedException;
use League\Route\Http\Exception\NotFoundException;
use League\Route\RouteCollection;
use League\Route\Strategy\UriStrategy;

// ... (Server creation) ...

    $router = new RouteCollection();
    $router->setStrategy(new UriStrategy());
    require __DIR__ . "/routes.php";
    $dispatcher = $router->getDispatcher();

    try {
        $result = $dispatcher->dispatch($request->getMethod(), $request->getRequestTarget());
        $status = 200;
        $content = $result->getContent();
    } catch (NotFoundException $e) {
        $status = 404;
        $content = "not found";
    } catch (MethodNotAllowedException $e) {
        $status = 405;
        $content = "method not allowed";
    }

    // ... (Response creation and sending) ...

A sample routes.php:

$router->addRoute("GET", "/home", function () {
    return "hello world";
});

Rendering Complex Views with League\Plates

For complex views, use League\Plates:

composer require league/plates

Implement templating (example snippets from templates/layout.php and templates/home.php, and updated routes.php are omitted for brevity but follow the original example's structure).

Performance Benchmarks and Conclusion

The original article includes performance benchmarks demonstrating the server's capability to handle a significant number of concurrent requests. These benchmarks should be considered in the context of the specific hardware and conditions under which they were run. The key takeaway is the potential for high performance with Icicle's asynchronous model. The article concludes by encouraging experimentation and community discussion. The updated benchmarks provided by the Icicle author are also included. The FAQ section further clarifies various aspects of using Icicle for server development.