symfony/symfony

Symfony is a leading open-source PHP web development framework and a set of reusable PHP components. Developed and maintained by SensioLabs, 'symfony/symfony' refers to the entire framework or the main meta-package that pulls in all essential Symfony components. It provides a robust architecture for building scalable, high-performance web applications, APIs, microservices, and console applications.

Key Concepts and Features:

1. Component-Based Architecture: Symfony is built as a collection of decoupled, reusable PHP components (e.g., HttpFoundation, Routing, DependencyInjection, EventDispatcher, Console, Twig, DoctrineBridge). These components can be used independently in any PHP project, offering immense flexibility.
2. Full-Stack Framework: While its components are independent, Symfony as a framework provides a full-stack solution with an MVC (Model-View-Controller) architecture, offering tools for routing, database interaction (via Doctrine ORM/DBAL), form handling, security, templating (Twig), and more.
3. Performance: Symfony is designed for performance, leveraging features like bytecode caching, compilation, and an optimized architecture. It promotes best practices for efficient application development.
4. Extensibility (Bundles): Symfony's plugin system is called 'Bundles'. A Bundle is a structured set of files (PHP classes, configuration, templates, assets) that implements a specific feature. Applications themselves are structured as bundles, and third-party functionalities are added as bundles, making it highly modular and extensible.
5. Dependency Injection: A core principle, the Dependency Injection Container (DIC) manages object creation and dependencies, making code more testable, maintainable, and flexible.
6. HTTP Kernel: At its heart, Symfony's request-response cycle is managed by the HTTP Kernel component. It takes an incoming `Request` object and returns a `Response` object.
7. Routing: Defines how URLs map to controllers, supporting flexible URL patterns and generation.
8. Forms: A powerful component for creating, processing, and validating forms securely.
9. Security: Comprehensive security features including authentication, authorization, and protection against common web vulnerabilities.
10. Community & Documentation: Symfony boasts a large, active community and extensive, high-quality documentation, making it easier for developers to learn and find solutions.

Purpose:
Symfony is ideal for developing complex, enterprise-level applications where scalability, maintainability, and extensibility are crucial. Its component-based nature also makes it suitable for integrating specific functionalities into existing projects or building custom micro-frameworks.

<?php

// To run this example:
// 1. Ensure you have Composer installed.
// 2. Create a new directory for your project.
// 3. Open your terminal in that directory and run:
//    composer require symfony/http-foundation
// 4. Save this code as 'index.php' in your project directory.
// 5. Run it via a PHP development server: php -S localhost:8000
// 6. Access in browser: http://localhost:8000/hello?name=Symfony or http://localhost:8000/submit (with POST data)

require __DIR__ . '/vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

// 1. Create a Request object from global PHP variables (e.g., $_GET, $_POST, $_SERVER)
// This object encapsulates all information about the current HTTP request.
$request = Request::createFromGlobals();

// 2. Process the request based on its path and method
if ($request->getPathInfo() === '/hello' && $request->isMethod('GET')) {
    // Get the 'name' parameter from the query string (e.g., /hello?name=John)
    // Default to 'World' if not provided.
    $name = $request->query->get('name', 'World');

    // 3. Create a Response object with the content, status code, and headers
    // This object encapsulates the HTTP response that will be sent back to the client.
    $response = new Response(
        sprintf('<h1>Hello %s!</h1>', htmlspecialchars($name)),
        Response::HTTP_OK, // 200 OK
        ['Content-Type' => 'text/html']
    );
} else if ($request->getPathInfo() === '/submit' && $request->isMethod('POST')) {
    // Example for handling a POST request
    // You could send POST data using tools like Postman or a simple HTML form.
    $data = $request->request->all(); // Get all POST data as an array
    $response = new Response(
        '<h2>Submitted Data:</h2><pre>' . htmlspecialchars(json_encode($data, JSON_PRETTY_PRINT)) . '</pre>',
        Response::HTTP_OK,
        ['Content-Type' => 'text/html']
    );
} else {
    // Handle requests that don't match our defined paths (e.g., 404 Not Found)
    $response = new Response(
        '<h1>404 Not Found</h1><p>Try visiting <a href="/hello?name=Symfony">/hello?name=Symfony</a></p>',
        Response::HTTP_NOT_FOUND, // 404 Not Found
        ['Content-Type' => 'text/html']
    );
}

// 4. Send the response back to the client's browser
$response->send();

?>