Build your own PHP Framework with Symfony Components

This tutorial demonstrates building a minimal PHP framework using Symfony components. While not exhaustive, it covers the core elements for a functional application. For deeper dives, consult the official Symfony documentation.

Key Concepts:

This tutorial leverages Symfony components to build a flexible framework. It uses HttpFoundation for managing HTTP requests and responses, replacing standard PHP globals. The Routing component enables dynamic URL handling, and the EventDispatcher component facilitates modularity and extensibility via the Observer pattern. Finally, the HttpKernel component streamlines request processing and response generation.

Project Setup:

Begin with a basic index.php file and install necessary components using Composer:

php composer.phar require symfony/http-foundation symfony/http-kernel symfony/routing symfony/event-dispatcher

HttpFoundation:

HttpFoundation provides Request and Response classes. Initially, index.php might look like this (using globals):

switch($_SERVER['PATH_INFO']) {
    case '/': echo 'Home'; break;
    case '/about': echo 'About'; break;
    default: echo 'Not Found!';
}

This is improved by using HttpFoundation:

require 'vendor/autoload.php';
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$request = Request::createFromGlobals();
$response = new Response();

switch ($request->getPathInfo()) {
    case '/': $response->setContent('Home'); break;
    case '/about': $response->setContent('About'); break;
    default: $response->setContent('Not Found!')->setStatusCode(Response::HTTP_NOT_FOUND);
}

$response->send();

HttpKernel:

To encapsulate framework logic, create a Core class (e.g., lib/Framework/Core.php):

<?php
namespace Framework;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;

class Core implements HttpKernelInterface {
    public function handle(Request $request, $type = HttpKernelInterface::MASTER_REQUEST, $catch = true) {
        switch ($request->getPathInfo()) {
            case '/': return new Response('Home');
            case '/about': return new Response('About');
            default: return new Response('Not Found!', Response::HTTP_NOT_FOUND);
        }
    }
}

Update index.php:

require 'lib/Framework/Core.php';
$request = Request::createFromGlobals();
$app = new Framework\Core();
$response = $app->handle($request);
$response->send();

Improved Routing (Routing Component):

The Core class is enhanced with a routing system using the Routing component:

<?php
// ... (previous code) ...
use Symfony\Component\Routing\Matcher\UrlMatcher;
use Symfony\Component\Routing\RequestContext;
use Symfony\Component\Routing\RouteCollection;
use Symfony\Component\Routing\Route;
use Symfony\Component\Routing\Exception\ResourceNotFoundException;

class Core implements HttpKernelInterface {
    protected $routes;

    public function __construct() { $this->routes = new RouteCollection(); }

    public function handle(Request $request) {
        $context = new RequestContext();
        $context->fromRequest($request);
        $matcher = new UrlMatcher($this->routes, $context);

        try {
            $attributes = $matcher->match($request->getPathInfo());
            $controller = $attributes['controller'];
            unset($attributes['controller']);
            return call_user_func_array($controller, $attributes);
        } catch (ResourceNotFoundException $e) {
            return new Response('Not Found!', Response::HTTP_NOT_FOUND);
        }
    }

    public function map($path, $controller) {
        $this->routes->add($path, new Route($path, ['controller' => $controller]));
    }
}

Routes are now defined in index.php:

$app->map('/', function() { return new Response('Home'); });
$app->map('/about', function() { return new Response('About'); });
// ...

EventDispatcher:

The EventDispatcher component adds event handling capabilities. Add an on method and a fire method to the Core class and a RequestEvent class. (Implementation details omitted for brevity, but similar to the example in the original input). Listeners can be added using $app->on('request', ...);.

This framework provides a foundation for building more complex applications using Symfony's power and flexibility. Remember to consult the official Symfony documentation for more advanced features and component details.

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