Symfony Kernel Laravel Package

Getting Started

Minimal Steps

1. Installation

   composer require dpoposki/symfony-kernel
   

   Register the bundle in config/bundles.php (Symfony) or AppKernel.php (legacy):

   return [
       // ...
       Dpoposki\SymfonyKernel\DpoposkiSymfonyKernelBundle::class => ['all' => true],
   ];
   

2. First Use Case Leverage the kernel for custom request handling or bootstrapping logic. Example:

   use Symfony\Component\HttpKernel\KernelInterface;
   use Dpoposki\SymfonyKernel\Kernel\CustomKernel;
   
   class AppKernel extends CustomKernel {
       public function __construct($environment, $debug) {
           parent::__construct($environment, $debug);
       }
   
       // Override to add custom bundles or logic
       protected function build(KernelInterface $kernel) {
           $kernel->getContainer()->loadFromExtension('framework', [
               'secret' => '%env(APP_SECRET)%',
           ]);
       }
   }
   

3. Where to Look First

   • src/Kernel/CustomKernel.php: Core kernel logic.
   • src/DependencyInjection/: Configuration and extensions.
   • tests/: Example use cases and edge scenarios.

Implementation Patterns

Workflows

1. Extending the Kernel Override CustomKernel to inject custom logic:

   class AppKernel extends CustomKernel {
       public function registerBundles() {
           $bundles = parent::registerBundles();
           $bundles[] = new \Acme\CustomBundle\AcmeCustomBundle();
           return $bundles;
       }
   }
   

2. Dynamic Configuration Use the kernel’s build() method to modify container parameters dynamically:

   protected function build(KernelInterface $kernel) {
       $container = $kernel->getContainer();
       $container->setParameter('custom.param', 'dynamic_value');
   }
   

3. Event Listeners Attach listeners to kernel events (e.g., kernel.request):

   use Symfony\Component\HttpKernel\Event\GetResponseEvent;
   
   $kernel->getContainer()->get('event_dispatcher')->addListener(
       'kernel.request',
       function (GetResponseEvent $event) {
           // Custom logic here
       }
   );
   

Integration Tips

• Laravel-Symfony Hybrid Apps: Use this kernel to bridge Symfony components (e.g., HTTP client, forms) into Laravel.
• Microservices: Deploy as a standalone Symfony kernel for API endpoints while sharing logic with Laravel.
• Testing: Mock the kernel in PHPUnit:

  $kernel = $this->createMock(CustomKernel::class);
  $kernel->method('getContainer')->willReturn($container);
  

Gotchas and Tips

Pitfalls

1. Bundle Registration Order

   • Symfony bundles must be registered before the kernel boots. Use registerBundles() carefully to avoid BundleNotFoundException.
   • Fix: Ensure all dependencies are installed and autoloaded.

2. Circular Dependencies

   • Overriding build() or registerBundles() can create circular references if not managed.
   • Fix: Use dependency injection or lazy-loading where possible.

3. Environment Variables

   • The kernel assumes Symfony’s %env() syntax. For Laravel, preload env vars:

     putenv('APP_ENV=' . getenv('APP_ENV'));
     

Debugging

• Kernel Boot Errors: Check var/log/dev.log (Symfony) or Laravel’s storage/logs/laravel.log.
• Container Dumping: Dump the container to inspect services:

  $container->get('debug.dump_service');
  

Extension Points

1. Custom Console Commands Extend the kernel to add CLI tools:

   $kernel->getContainer()->set('console.command.my_command', function () {
       return new MyCommand();
   });
   

2. Middleware Integration Add Symfony middleware to Laravel’s pipeline:

   $kernel->getContainer()->get('http_kernel')->pushMiddleware(new MyMiddleware());
   

3. Configuration Overrides Merge custom config in build():

   $container->loadFromExtension('framework', [
       'router' => ['resource' => '%kernel.project_dir%/config/routes.yaml'],
   ]);
   

Pro Tips

• Performance: Cache the kernel instance if reused across requests (e.g., in CLI scripts).
• Security: Validate environment variables in build():

  if (empty($container->getParameter('app.secret'))) {
      throw new \RuntimeException('APP_SECRET is required!');
  }