Controller

Controller

A controller is a PHP function you create that reads information from the Symfony's 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 you can dream up. The controller executes whatever arbitrary logic your application needs to render the content of a page.

See how simple this is by looking at a Symfony controller in action. This renders a page that prints a lucky (random) number:

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

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Symfony\Component\HttpFoundation\Response;

class LuckyController
{
    /**
     * @Route("/lucky/number")
     */
    public function numberAction()
    {
        $number = mt_rand(0, 100);

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

But in the real world, your controller will probably do a lot of work in order to create the response. It might read information from the request, load a database resource, send an email or set information on the user's session. But in all cases, the controller will eventually return the Response object that will be delivered back to the client.

Tip

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

A Simple Controller

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

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

use Symfony\Component\HttpFoundation\Response;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;

class LuckyController
{
    /**
     * @Route("/lucky/number/{max}")
     */
    public function numberAction($max)
    {
        $number = mt_rand(0, $max);

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

The controller is the numberAction() method, which lives inside a 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 should end in the word Controller (this isn't required, but some shortcuts rely on this).
  • line 12: Each action method in a controller class is suffixed with Action (again, this isn't required, but some shortcuts rely on this). This method is allowed to have a $name argument thanks to the {name} wildcard in the route.
  • line 16: 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}") annotation.

To see your page, go to this URL in your browser:

For more information on routing, see Routing.

The Base Controller Class & Services

For convenience, Symfony comes with an optional base Controller class. If you extend it, this won't change anything about how your controller works, but you'll get access to a number of helper methods and the service container (see Accessing other Services): an array-like object that gives you access to every useful object in the system. These useful objects are called services, and Symfony ships with a service object that can render Twig templates, another that can log messages and many more.

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

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

use Symfony\Bundle\FrameworkBundle\Controller\Controller;

class LuckyController extends Controller
{
    // ...
}

Helper methods are just shortcuts to using core Symfony functionality that's available to you with or without the use of the base Controller class. A great way to see the core functionality in action is to look in the Controller class.

Generating URLs

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

$url = $this->generateUrl('blog_show', array('slug' => 'slug-value'));

Redirecting

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

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public function indexAction()
{
    // redirect to the "homepage" route
    return $this->redirectToRoute('homepage');

    // do a permanent - 301 redirect
    return $this->redirectToRoute('homepage', array(), 301);

    // redirect to a route with parameters
    return $this->redirectToRoute('blog_show', array('slug' => 'my-page'));

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

For more information, see the Routing chapter.

Tip

The redirectToRoute() method is simply a shortcut that creates a Response object that specializes in redirecting the user. It's equivalent to:

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use Symfony\Component\HttpFoundation\RedirectResponse;

public function indexAction()
{
    return new RedirectResponse($this->generateUrl('homepage'));
}

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:

// renders app/Resources/views/lucky/number.html.twig
return $this->render('lucky/number.html.twig', array('name' => $name));

Templates can also live in deeper sub-directories. Just try to avoid creating unnecessarily deep structures:

// renders app/Resources/views/lottery/lucky/number.html.twig
return $this->render('lottery/lucky/number.html.twig', array(
    'name' => $name
));

The Symfony templating system and Twig are explained more in the Creating and Using Templates chapter.

Accessing other Services

Symfony comes packed with a lot of useful objects, called services. These are used for rendering templates, sending emails, querying the database and any other "work" you can think of. When you install a new bundle, it probably brings in even more services.

When extending the base controller class, you can access any Symfony service via the get() method of the Controller class. Here are several common services you might need:

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$templating = $this->get('templating');

$router = $this->get('router');

$mailer = $this->get('mailer');

What other services exist? To list all services, use the debug:container console command:

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$ php bin/console debug:container

For more information, see the Service Container chapter.

Tip

To get a container configuration parameter, use the getParameter() method:

$from = $this->getParameter('app.mailer.from');

Managing Errors and 404 Pages

When things are not found, you should play well with the HTTP protocol and return a 404 response. To do this, you'll throw a special type of exception. If you're extending the base Controller class, do the following:

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public function indexAction()
{
    // retrieve the object from database
    $product = ...;
    if (!$product) {
        throw $this->createNotFoundException('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.

Of course, you're free to throw any Exception class in your controller - Symfony will automatically return a 500 HTTP response code.

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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 using the app_dev.php front controller - see The imports Key: Loading other Configuration Files).

You'll want to customize the error page your user sees. To do that, 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? All of that information is stored in Symfony's Request object. To get it in your controller, just add it as an argument and type-hint it with the ``Request`` class:

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use Symfony\Component\HttpFoundation\Request;

public function indexAction($firstName, $lastName, Request $request)
{
    $page = $request->query->get('page', 1);

    // ...
}

Keep reading for more information about using the Request object.

Managing the Session

Symfony provides a nice session object that you can use to store information about the user between requests. By default, Symfony stores the attributes in a cookie by using native PHP sessions.

To retrieve the session, call getSession() method on the Request object. This method returns a SessionInterface with easy methods for storing and fetching things from the session:

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use Symfony\Component\HttpFoundation\Request;

public function indexAction(Request $request)
{
    $session = $request->getSession();

    // store an attribute for reuse during a later user request
    $session->set('foo', 'bar');

    // get the attribute set by another controller in another request
    $foobar = $session->get('foobar');

    // use a default value if the attribute doesn't exist
    $filters = $session->get('filters', array());
}

Stored attributes remain in the session for the remainder of that user's session.

Flash Messages

You can also 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;

public function updateAction(Request $request)
{
    // ...

    if ($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(...);
}

After processing the request, the controller sets a flash message in the session and then redirects. The message key (notice in this example) can be anything: you'll use this key to retrieve the message.

In the template of the next page (or even better, in your base layout template), read any flash messages from the session:

  • Twig
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    {# app/Resources/views/base.html.twig #}
    {% for flash_message in app.session.flashBag.get('notice') %}
        <div class="flash-notice">
            {{ flash_message }}
        </div>
    {% endfor %}
    
  • PHP
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    <!-- app/Resources/views/base.html.php -->
    <?php foreach ($view['session']->getFlash('notice') as $message): ?>
        <div class="flash-notice">
            <?php echo "<div class='flash-error'>$message</div>" ?>
        </div>
    <?php endforeach ?>
    

Note

It's common to use notice, warning and error as the keys of the different types of flash messages, but you can use any key that fits your needs.

Tip

You can use the peek() method instead to retrieve the message while keeping it in the bag.

The Request and Response Object

As mentioned earlier, the framework 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;

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

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

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

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

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

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

    // retrieve 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 also a public headers property. This is a ResponseHeaderBag that has some nice methods for getting and setting response headers. The header names are normalized so that using Content-Type is equivalent to content-type or even content_type.

The only requirement for a controller is to return a Response object. The Response class is an abstraction around the HTTP response - the text-based message filled with headers and content that's sent back to the client:

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use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\JsonResponse;

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

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

There are special classes that make certain kinds of responses easier:

Now that you know the basics you can continue your research on Symfony Request and Response object in the HttpFoundation component documentation.

JSON Helper

3.1The json() helper was introduced in Symfony 3.1.

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

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

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

If the serializer service is enabled in your application, contents passed to json() are encoded with it. Otherwise, the json_encode function is used.

File helper

New in version 3.2: The file() helper was introduced in Symfony 3.2.

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

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public function fileAction()
{
    // 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 fileAction()
{
    // 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

Whenever you create a page, you'll ultimately need to write some code that contains the logic for that page. In Symfony, this is called a controller, and it's a PHP function where you can do anything in order to return the final Response object that will be returned to the user.

To make life easier, you'll probably extend the base Controller class because this gives two things:

  1. Shortcut methods (like render() and redirectToRoute);
  2. Access to all of the useful objects (services) in the system via the get() method.

In other chapters, 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.

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