Building your own Framework with the MicroKernelTrait ===================================================== The default ``Kernel`` class included in Symfony applications uses a :class:`Symfony\\Bundle\\FrameworkBundle\\Kernel\\MicroKernelTrait` to configure the bundles, the routes and the service container in the same class. This micro-kernel approach is flexible, allowing you to control your application structure and features. A Single-File Symfony Application --------------------------------- Start with a completely empty directory and install these Symfony components via Composer: .. code-block:: terminal $ composer require symfony/config symfony/http-kernel \ symfony/http-foundation symfony/routing \ symfony/dependency-injection symfony/framework-bundle Next, create an ``index.php`` file that defines the kernel class and executes it:: // index.php use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait; use Symfony\Bundle\FrameworkBundle\Routing\Loader\Configurator\RoutingConfigurator; use Symfony\Component\Config\Loader\LoaderInterface; use Symfony\Component\DependencyInjection\ContainerBuilder; use Symfony\Component\HttpFoundation\JsonResponse; use Symfony\Component\HttpFoundation\Request; use Symfony\Component\HttpKernel\Kernel as BaseKernel; require __DIR__.'/vendor/autoload.php'; class Kernel extends BaseKernel { use MicroKernelTrait; public function registerBundles() { return [ new Symfony\Bundle\FrameworkBundle\FrameworkBundle() ]; } protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader) { // PHP equivalent of config/packages/framework.yaml $c->loadFromExtension('framework', [ 'secret' => 'S0ME_SECRET' ]); } protected function configureRoutes(RoutingConfigurator $routes) { // kernel is a service that points to this class // optional 3rd argument is the route name $routes->add('/random/{limit}', 'kernel::randomNumber'); } public function randomNumber($limit) { return new JsonResponse([ 'number' => random_int(0, $limit), ]); } } $kernel = new Kernel('dev', true); $request = Request::createFromGlobals(); $response = $kernel->handle($request); $response->send(); $kernel->terminate($request, $response); That's it! To test it, start the :doc:`Symfony Local Web Server `: .. code-block:: terminal $ symfony server:start Then see the JSON response in your browser: http://localhost:8000/random/10 The Methods of a "Micro" Kernel ------------------------------- When you use the ``MicroKernelTrait``, your kernel needs to have exactly three methods that define your bundles, your services and your routes: **registerBundles()** This is the same ``registerBundles()`` that you see in a normal kernel. **configureContainer(ContainerBuilder $c, LoaderInterface $loader)** This method builds and configures the container. In practice, you will use ``loadFromExtension`` to configure different bundles (this is the equivalent of what you see in a normal ``config/packages/*`` file). You can also register services directly in PHP or load external configuration files (shown below). **configureRoutes(RoutingConfigurator $routes)** Your job in this method is to add routes to the application. The ``RoutingConfigurator`` has methods that make adding routes in PHP more fun. You can also load external routing files (shown below). Advanced Example: Twig, Annotations and the Web Debug Toolbar ------------------------------------------------------------- The purpose of the ``MicroKernelTrait`` is *not* to have a single-file application. Instead, its goal to give you the power to choose your bundles and structure. First, you'll probably want to put your PHP classes in an ``src/`` directory. Configure your ``composer.json`` file to load from there: .. code-block:: json { "require": { "...": "..." }, "autoload": { "psr-4": { "App\\": "src/" } } } Then, run ``composer dump-autoload`` to dump your new autoload config. Now, suppose you want to use Twig and load routes via annotations. Instead of putting *everything* in ``index.php``, create a new ``src/Kernel.php`` to hold the kernel. Now it looks like this:: // src/Kernel.php namespace App; use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait; use Symfony\Bundle\FrameworkBundle\Routing\Loader\Configurator\RoutingConfigurator; use Symfony\Component\Config\Loader\LoaderInterface; use Symfony\Component\DependencyInjection\ContainerBuilder; use Symfony\Component\HttpKernel\Kernel as BaseKernel; class Kernel extends BaseKernel { use MicroKernelTrait; public function registerBundles() { $bundles = [ new \Symfony\Bundle\FrameworkBundle\FrameworkBundle(), new \Symfony\Bundle\TwigBundle\TwigBundle(), ]; if ($this->getEnvironment() == 'dev') { $bundles[] = new Symfony\Bundle\WebProfilerBundle\WebProfilerBundle(); } return $bundles; } protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader) { $loader->load(__DIR__.'/../config/framework.yaml'); // configure WebProfilerBundle only if the bundle is enabled if (isset($this->bundles['WebProfilerBundle'])) { $c->loadFromExtension('web_profiler', [ 'toolbar' => true, 'intercept_redirects' => false, ]); } } protected function configureRoutes(RoutingConfigurator $routes) { // import the WebProfilerRoutes, only if the bundle is enabled if (isset($this->bundles['WebProfilerBundle'])) { $routes->import('@WebProfilerBundle/Resources/config/routing/wdt.xml', '/_wdt'); $routes->import('@WebProfilerBundle/Resources/config/routing/profiler.xml', '/_profiler'); } // load the annotation routes $routes->import(__DIR__.'/../src/Controller/', '/', 'annotation'); } // optional, to use the standard Symfony cache directory public function getCacheDir() { return __DIR__.'/../var/cache/'.$this->getEnvironment(); } // optional, to use the standard Symfony logs directory public function getLogDir() { return __DIR__.'/../var/log'; } } Before continuing, run this command to add support for the new dependencies: .. code-block:: terminal $ composer require symfony/yaml symfony/twig-bundle symfony/web-profiler-bundle doctrine/annotations Unlike the previous kernel, this loads an external ``config/framework.yaml`` file, because the configuration started to get bigger: .. configuration-block:: .. code-block:: yaml # config/framework.yaml framework: secret: S0ME_SECRET profiler: { only_exceptions: false } .. code-block:: xml .. code-block:: php // config/framework.php $container->loadFromExtension('framework', [ 'secret' => 'S0ME_SECRET', 'profiler' => [ 'only_exceptions' => false, ], ]); This also loads annotation routes from an ``src/Controller/`` directory, which has one file in it:: // src/Controller/MicroController.php namespace App\Controller; use Symfony\Bundle\FrameworkBundle\Controller\AbstractController; use Symfony\Component\Routing\Annotation\Route; class MicroController extends AbstractController { /** * @Route("/random/{limit}") */ public function randomNumber($limit) { $number = random_int(0, $limit); return $this->render('micro/random.html.twig', [ 'number' => $number, ]); } } Template files should live in the ``templates/`` directory at the root of your project. This template lives at ``templates/micro/random.html.twig``: .. code-block:: html+twig Random action

{{ number }}

Finally, you need a front controller to boot and run the application. Create a ``public/index.php``:: // public/index.php use App\Kernel; use Doctrine\Common\Annotations\AnnotationRegistry; use Symfony\Component\HttpFoundation\Request; $loader = require __DIR__.'/../vendor/autoload.php'; // auto-load annotations AnnotationRegistry::registerLoader([$loader, 'loadClass']); $kernel = new Kernel('dev', true); $request = Request::createFromGlobals(); $response = $kernel->handle($request); $response->send(); $kernel->terminate($request, $response); That's it! This ``/random/10`` URL will work, Twig will render, and you'll even get the web debug toolbar to show up at the bottom. The final structure looks like this: .. code-block:: text your-project/ ├─ config/ │ └─ framework.yaml ├─ public/ | └─ index.php ├─ src/ | ├─ Controller | | └─ MicroController.php | └─ Kernel.php ├─ templates/ | └─ micro/ | └─ random.html.twig ├─ var/ | ├─ cache/ │ └─ log/ ├─ vendor/ │ └─ ... ├─ composer.json └─ composer.lock As before you can use the :doc:`Symfony Local Web Server `: .. code-block:: terminal cd public/ $ symfony server:start Then visit the page in your browser: http://localhost:8000/random/10