What is Symfony?

Symfony is a mature, modular PHP framework used by enterprises and as the foundation for Laravel, Drupal, and API Platform. Its reusable components can be adopted independently.

Creating a Project 

  composer create-project symfony/skeleton myapp
cd myapp
composer require webapp
symfony server:start

Routing and Controllers 

  // src/Controller/HelloController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Attribute\Route;

class HelloController extends AbstractController
{
    #[Route('/hello/{name}', name: 'app_hello')]
    public function hello(string $name): Response
    {
        return $this->render('hello.html.twig', ['name' => $name]);
    }
}

Twig Templates 

  {# templates/hello.html.twig #}
<h1>Hello, {{ name }}!</h1>

Doctrine ORM 

  composer require symfony/orm-pack
php bin/console make:entity Product
php bin/console make:migration
php bin/console doctrine:migrations:migrate
  
  // src/Entity/Product.php
#[ORM\Entity]
class Product
{
    #[ORM\Id, ORM\GeneratedValue, ORM\Column]
    private ?int $id = null;

    #[ORM\Column(length: 255)]
    private string $name = '';
}
  
  $product = new Product();
$product->setName('Widget');
$entityManager->persist($product);
$entityManager->flush();

Dependency Injection

Symfony’s service container wires dependencies automatically:

  public function __construct(
    private ProductRepository $productRepository
) {}

Configure services in config/services.yaml.

Console Commands 

  php bin/console make:command app:greet
php bin/console list
php bin/console cache:clear

Symfony vs Laravel

Aspect Symfony Laravel
Philosophy Components-first, explicit Convention over configuration
Learning curve Steeper Gentler
Best for Enterprise, long-term APIs Rapid web apps, startups
ORM Doctrine Eloquent

Both are excellent choices — Symfony excels when you need fine-grained control and reusable components.

Symfony Flex and Recipes

Modern Symfony projects use Flex to auto-configure bundles. When you run composer require symfony/mailer, Flex adds config files and env variables automatically.

Validation Component 

  use Symfony\Component\Validator\Validation;

$validator = Validation::createValidator();
$violations = $validator->validate($email, [new Email(), new NotBlank()]);

foreach ($violations as $violation) {
    echo $violation->getMessage();
}

Event System

Symfony’s event dispatcher decouples components:

  // src/EventSubscriber/OrderSubscriber.php
class OrderSubscriber implements EventSubscriberInterface {
    public static function getSubscribedEvents(): array {
        return [OrderPlacedEvent::class => 'onOrderPlaced'];
    }

    public function onOrderPlaced(OrderPlacedEvent $event): void {
        // Send confirmation email
    }
}

Environment Configuration

Symfony uses .env files with %env(VAR_NAME)% in YAML config:

  # config/packages/doctrine.yaml
doctrine:
    dbal:
        url: '%env(resolve:DATABASE_URL)%'

Run php bin/console debug:config doctrine to inspect resolved settings.

Testing with PHPUnit 

  composer require --dev symfony/test-pack
php bin/phpunit

Symfony provides WebTestCase for functional HTTP tests and KernelTestCase for service container tests.

Common Pitfalls

  • Clearing cache after config changes: php bin/console cache:clear.
  • Forgetting to warm cache in production after deploy.
  • Mixing annotation and attribute routing during migration — pick one style per project.