Controller

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Controller

A controller is a PHP function you create that reads information from the Request object and creates and returns a Response object. The response could be an HTML page, JSON, XML, a file download, a redirect, a 404 error or anything else. The controller runs whatever arbitrary logic your application needs to render the content of a page.

Tip

If you haven't already created your first working page, check out Create your First Page in Symfony and then come back!

A Basic Controller

While a controller can be any PHP callable (function, method on an object, or a Closure), a controller is usually a method inside a controller class:

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

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;

class LuckyController
{
    #[Route('/lucky/number/{max}', name: 'app_lucky_number')]
    public function number(int $max): Response
    {
        $number = random_int(0, $max);

        return new Response(
            '<html><body>Lucky number: '.$number.'</body></html>'
        );
    }
}

The controller is the number() method, which lives inside the controller class LuckyController.

This controller is pretty straightforward:

  • line 2: Symfony takes advantage of PHP's namespace functionality to namespace the entire controller class.
  • line 4: Symfony again takes advantage of PHP's namespace functionality: the use keyword imports the Response class, which the controller must return.
  • line 7: The class can technically be called anything, but it's suffixed with Controller by convention.
  • line 10: The action method is allowed to have a $max argument thanks to the {max} wildcard in the route.
  • line 14: The controller creates and returns a Response object.

Mapping a URL to a Controller

In order to view the result of this controller, you need to map a URL to it via a route. This was done above with the #[Route('/lucky/number/{max}')] route attribute.

To see your page, go to this URL in your browser: http://localhost:8000/lucky/number/100

For more information on routing, see Routing.

The Base Controller Class & Services

To aid development, Symfony comes with an optional base controller class called AbstractController. It can be extended to gain access to helper methods.

Add the use statement atop your controller class and then modify LuckyController to extend it:

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

+ use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;

- class LuckyController
+ class LuckyController extends AbstractController
  {
      // ...
  }

That's it! You now have access to methods like $this->render() and many others that you'll learn about next.

Generating URLs

The generateUrl() method is just a helper method that generates the URL for a given route:

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$url = $this->generateUrl('app_lucky_number', ['max' => 10]);

Redirecting

If you want to redirect the user to another page, use the redirectToRoute() and redirect() methods:

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use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpFoundation\Response;

// ...
public function index(): RedirectResponse
{
    // redirects to the "homepage" route
    return $this->redirectToRoute('homepage');

    // redirectToRoute is a shortcut for:
    // return new RedirectResponse($this->generateUrl('homepage'));

    // does a permanent HTTP 301 redirect
    return $this->redirectToRoute('homepage', [], 301);
    // if you prefer, you can use PHP constants instead of hardcoded numbers
    return $this->redirectToRoute('homepage', [], Response::HTTP_MOVED_PERMANENTLY);

    // redirect to a route with parameters
    return $this->redirectToRoute('app_lucky_number', ['max' => 10]);

    // redirects to a route and maintains the original query string parameters
    return $this->redirectToRoute('blog_show', $request->query->all());

    // redirects to the current route (e.g. for Post/Redirect/Get pattern):
    return $this->redirectToRoute($request->attributes->get('_route'));

    // redirects externally
    return $this->redirect('http://symfony.com/doc');
}

Caution

The redirect() method does not check its destination in any way. If you redirect to a URL provided by end-users, your application may be open to the unvalidated redirects security vulnerability.

Rendering Templates

If you're serving HTML, you'll want to render a template. The render() method renders a template and puts that content into a Response object for you:

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// renders templates/lucky/number.html.twig
return $this->render('lucky/number.html.twig', ['number' => $number]);

Templating and Twig are explained more in the Creating and Using Templates article.

Fetching Services

Symfony comes packed with a lot of useful classes and functionalities, called services. These are used for rendering templates, sending emails, querying the database and any other "work" you can think of.

If you need a service in a controller, type-hint an argument with its class (or interface) name. Symfony will automatically pass you the service you need:

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use Psr\Log\LoggerInterface;
use Symfony\Component\HttpFoundation\Response;
// ...

#[Route('/lucky/number/{max}')]
public function number(int $max, LoggerInterface $logger): Response
{
    $logger->info('We are logging!');
    // ...
}

Awesome!

What other services can you type-hint? To see them, use the debug:autowiring console command:

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$ php bin/console debug:autowiring

If you need control over the exact value of an argument, you can bind the argument by its name:

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# config/services.yaml
services:
    # ...

    # explicitly configure the service
    App\Controller\LuckyController:
        tags: [controller.service_arguments]
        bind:
            # for any $logger argument, pass this specific service
            $logger: '@monolog.logger.doctrine'
            # for any $projectDir argument, pass this parameter value
            $projectDir: '%kernel.project_dir%'

Like with all services, you can also use regular constructor injection in your controllers.

For more information about services, see the Service Container article.

Generating Controllers

To save time, you can install Symfony Maker and tell Symfony to generate a new controller class:

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$ php bin/console make:controller BrandNewController

created: src/Controller/BrandNewController.php
created: templates/brandnew/index.html.twig

If you want to generate an entire CRUD from a Doctrine entity, use:

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$ php bin/console make:crud Product

created: src/Controller/ProductController.php
created: src/Form/ProductType.php
created: templates/product/_delete_form.html.twig
created: templates/product/_form.html.twig
created: templates/product/edit.html.twig
created: templates/product/index.html.twig
created: templates/product/new.html.twig
created: templates/product/show.html.twig

Managing Errors and 404 Pages

When things are not found, you should return a 404 response. To do this, throw a special type of exception:

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use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;

// ...
public function index(): Response
{
    // retrieve the object from database
    $product = ...;
    if (!$product) {
        throw $this->createNotFoundException('The product does not exist');

        // the above is just a shortcut for:
        // throw new NotFoundHttpException('The product does not exist');
    }

    return $this->render(/* ... */);
}

The createNotFoundException() method is just a shortcut to create a special NotFoundHttpException object, which ultimately triggers a 404 HTTP response inside Symfony.

If you throw an exception that extends or is an instance of HttpException, Symfony will use the appropriate HTTP status code. Otherwise, the response will have a 500 HTTP status code:

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// this exception ultimately generates a 500 status error
throw new \Exception('Something went wrong!');

In every case, an error page is shown to the end user and a full debug error page is shown to the developer (i.e. when you're in "Debug" mode - see Configuring Symfony).

To customize the error page that's shown to the user, see the How to Customize Error Pages article.

The Request object as a Controller Argument

What if you need to read query parameters, grab a request header or get access to an uploaded file? That information is stored in Symfony's Request object. To access it in your controller, add it as an argument and type-hint it with the Request class:

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

public function index(Request $request): Response
{
    $page = $request->query->get('page', 1);

    // ...
}

Keep reading for more information about using the Request object.

Managing the Session

You can store special messages, called "flash" messages, on the user's session. By design, flash messages are meant to be used exactly once: they vanish from the session automatically as soon as you retrieve them. This feature makes "flash" messages particularly great for storing user notifications.

For example, imagine you're processing a form submission:

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

public function update(Request $request): Response
{
    // ...

    if ($form->isSubmitted() && $form->isValid()) {
        // do some sort of processing

        $this->addFlash(
            'notice',
            'Your changes were saved!'
        );
        // $this->addFlash() is equivalent to $request->getSession()->getFlashBag()->add()

        return $this->redirectToRoute(/* ... */);
    }

    return $this->render(/* ... */);
}

Reading for more information about using Sessions.

The Request and Response Object

As mentioned earlier, Symfony will pass the Request object to any controller argument that is type-hinted with the Request class:

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

public function index(Request $request): Response
{
    $request->isXmlHttpRequest(); // is it an Ajax request?

    $request->getPreferredLanguage(['en', 'fr']);

    // retrieves GET and POST variables respectively
    $request->query->get('page');
    $request->request->get('page');

    // retrieves SERVER variables
    $request->server->get('HTTP_HOST');

    // retrieves an instance of UploadedFile identified by foo
    $request->files->get('foo');

    // retrieves a COOKIE value
    $request->cookies->get('PHPSESSID');

    // retrieves an HTTP request header, with normalized, lowercase keys
    $request->headers->get('host');
    $request->headers->get('content-type');
}

The Request class has several public properties and methods that return any information you need about the request.

Like the Request, the Response object has a public headers property. This object is of the type ResponseHeaderBag and provides methods for getting and setting response headers. The header names are normalized. As a result, the name Content-Type is equivalent to the name content-type or content_type.

In Symfony, a controller is required to return a Response object:

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use Symfony\Component\HttpFoundation\Response;

// creates a simple Response with a 200 status code (the default)
$response = new Response('Hello '.$name, Response::HTTP_OK);

// creates a CSS-response with a 200 status code
$response = new Response('<style> ... </style>');
$response->headers->set('Content-Type', 'text/css');

To facilitate this, different response objects are included to address different response types. Some of these are mentioned below. To learn more about the Request and Response (and different Response classes), see the HttpFoundation component documentation.

Accessing Configuration Values

To get the value of any configuration parameter from a controller, use the getParameter() helper method:

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// ...
public function index(): Response
{
    $contentsDir = $this->getParameter('kernel.project_dir').'/contents';
    // ...
}

Returning JSON Response

To return JSON from a controller, use the json() helper method. This returns a JsonResponse object that encodes the data automatically:

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use Symfony\Component\HttpFoundation\JsonResponse;
// ...

public function index(): JsonResponse
{
    // returns '{"username":"jane.doe"}' and sets the proper Content-Type header
    return $this->json(['username' => 'jane.doe']);

    // the shortcut defines three optional arguments
    // return $this->json($data, $status = 200, $headers = [], $context = []);
}

If the serializer service is enabled in your application, it will be used to serialize the data to JSON. Otherwise, the json_encode function is used.

Streaming File Responses

You can use the file() helper to serve a file from inside a controller:

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use Symfony\Component\HttpFoundation\BinaryFileResponse;
// ...

public function download(): BinaryFileResponse
{
    // send the file contents and force the browser to download it
    return $this->file('/path/to/some_file.pdf');
}

The file() helper provides some arguments to configure its behavior:

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use Symfony\Component\HttpFoundation\File\File;
use Symfony\Component\HttpFoundation\ResponseHeaderBag;
// ...

public function download(): BinaryFileResponse
{
    // load the file from the filesystem
    $file = new File('/path/to/some_file.pdf');

    return $this->file($file);

    // rename the downloaded file
    return $this->file($file, 'custom_name.pdf');

    // display the file contents in the browser instead of downloading it
    return $this->file('invoice_3241.pdf', 'my_invoice.pdf', ResponseHeaderBag::DISPOSITION_INLINE);
}

Final Thoughts

In Symfony, a controller is usually a class method which is used to accept requests, and return a Response object. When mapped with a URL, a controller becomes accessible and its response can be viewed.

To facilitate the development of controllers, Symfony provides an AbstractController. It can be used to extend the controller class allowing access to some frequently used utilities such as render() and redirectToRoute(). The AbstractController also provides the createNotFoundException() utility which is used to return a page not found response.

In other articles, you'll learn how to use specific services from inside your controller that will help you persist and fetch objects from a database, process form submissions, handle caching and more.

Keep Going!

Next, learn all about rendering templates with Twig.

Learn more about Controllers

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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