Getting Started

Minimal Steps

Installation:
```
composer require symfony/framework-bundle
```
This package is typically included automatically when using symfony/symfony or symfony/flex.
First Use Case:
- Bootstrapping the Framework: The bundle is auto-registered in Symfony’s kernel. No manual configuration is required for basic usage.
- Dependency Injection: Leverage Symfony’s container to autowire services:
```
use Symfony\Component\HttpKernel\KernelInterface;

public function __construct(private KernelInterface $kernel) {}
```
- Routing: Define routes in config/routes.yaml or via annotations/attributes:
```
# config/routes.yaml
app_homepage:
    path: /
    controller: App\Controller\HomeController::index
```
Where to Look First:
- Documentation: Symfony FrameworkBundle Docs
- Configuration: config/packages/framework.yaml (auto-generated by Symfony Flex).
- Kernel: config/bundles.php (auto-configured).

Implementation Patterns

Core Workflows

Service Configuration:
- Use framework.yaml to configure core features like session, cache, or HTTP cache:
```
# config/packages/framework.yaml
framework:
    session:
        handler_id: cache.app
    http_cache:
        invalidation:
            enabled: true
```
- Environment-Specific Configs: Override settings per environment (e.g., config/packages/dev/framework.yaml).
Dependency Injection:
- Autowiring: Annotate constructors with types (e.g., RequestStack, RouterInterface).
- Tagging Services: Use tags for dynamic service binding (e.g., kernel.event_listener):
```
#[Tag('kernel.event_listener', ['event' => 'kernel.request'])]
class MyListener {}
```
Routing and Controllers:
- Attribute Routing (Symfony 5.3+):
```
#[Route('/profile', name: 'app_profile')]
public function profile(): Response {}
```
- Legacy Annotations: Migrate from @Route to attributes using useAttributeAsKey in framework.yaml:
```
framework:
    router:
        use_attribute_as_key: true
```

Testing:

Kernel Tests: Extend Symfony\Bundle\FrameworkBundle\Test\KernelTestCase:

use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;

class MyTest extends KernelTestCase {
    public function testSomething(): void {
        self::bootKernel();
        $client = static::createClient();
        $client->request('GET', '/');
    }
}

Mocking Services: Use self::$container to access services in tests.

Event Listeners/Subscribers:

services:
    App\EventListener\MyListener:
        tags: ['kernel.event_listener']

Subscribers:
```
tags: ['kernel.event_subscriber']
```

Console Commands:

Create commands in src/Command/ and tag them:

#[AsCommand(name: 'app:greet')]
class GreetCommand extends Command {}

Configuration Reference:
- Generate a reference config shape:
```
php bin/console config:dump-reference framework
```

Integration Tips

Bundle Integration: Use BundleInterface to create custom bundles with FrameworkBundle features.
Environment Variables: Access via %env(APP_SECRET)% in framework.yaml or .env files.
Debugging: Enable debug mode in .env (APP_DEBUG=1) and use the profiler (/_profiler).

Gotchas and Tips

Pitfalls

Caching Quirks:
- Cache Warmup: Run php bin/console cache:warmup after config changes. In tests, use self::bootKernel() to ensure a fresh container.
- Stale Containers: Avoid reusing the same kernel instance across tests (fixed in Symfony 6.4+ via KernelTestCase).
Routing Issues:
- Attribute vs. Annotation: Ensure use_attribute_as_key: true is set for attribute routing to work.
- Route Overrides: Prioritize YAML routes over annotations/attributes if conflicts arise.
Dependency Injection:
- Circular Dependencies: Use autowire: false and explicit binding if needed.
- Service Not Found: Verify the service is tagged or registered in services.yaml.
Session Handling:
- Mock Sessions: Use MockSessionStorage in tests:
```
$session = new Session();
$session->setStorage(new MockSessionStorage());
self::$container->set('session', $session);
```
- Cookie Lifetime: Ensure cookie_lifetime is set in framework.yaml for session cookies.
Configuration Merging:
- Duplicate Keys: Symfony merges configs left-to-right. Override defaults in config/packages/overrides.yaml.
- Reference Config: Use config:dump-reference to debug config shapes.
Testing Gotchas:
- HttpCache: Clear cache in KernelTestCase:
```
self::ensureKernelShutdown();
```
- Decorated Services: Mock decorated services explicitly in tests.
Console Commands:
- Missing Console Package: Ensure symfony/console is installed if using commands.
- Command Data Collector: Only enabled if the console package is present.

Debugging Tips

Dump Container Services:
```
php bin/console debug:container
```
Check Routes:
```
php bin/console debug:router
```
Environment Variables:
```
php bin/console debug:env
```
Configuration:
```
php bin/console debug:config framework
```
Event Dispatcher:
```
php bin/console debug:event-dispatcher
```

Extension Points

Custom Configurators:
- Implement ConfiguratorInterface for custom config validation/normalization.
Event Subscribers:
- Extend EventSubscriberInterface for kernel events (e.g., kernel.request).
HttpKernel Extensions:
- Override HttpKernelInterface for custom request/response handling.
Service Providers:
- Use CompilerPass to modify the container at compile time.
Routing Loaders:
- Create custom LoaderInterface implementations for dynamic routes.

Performance Tips

Cache Pools: Use cache.app for session storage to reduce database load.

HTTP Cache: Enable http_cache for static assets:

framework:
    http_cache:
        enabled: true

OpCache: Ensure OPcache is enabled for PHP bytecode caching.

Security Tips

CSRF Protection: Enable in framework.yaml:

framework:
    csrf_protection:
        enabled: true

HSTS: Configure in framework.yaml:

framework:
    http_client:
        headers:
            Strict-Transport-Security: "max-age=31536000; includeSubDomains"

CORS: Use nelmio/cors-bundle for cross-origin requests.

Framework Bundle Laravel Package