Making the Locale “Sticky” during a User’s Session

Prior to Symfony 2.1, the locale was stored in a session attribute called _locale. Since 2.1, it is stored in the Request, which means that it’s not “sticky” during a user’s request. In this article, you’ll learn how to make the locale of a user “sticky” so that once it’s set, that same locale will be used for every subsequent request.

Creating a LocaleListener

To simulate that the locale is stored in a session, you need to create and register a new event listener. The listener will look something like this. Typically, _locale is used as a routing parameter to signify the locale, though it doesn’t really matter how you determine the desired locale from the request:

// src/AppBundle/EventListener/LocaleListener.php
namespace AppBundle\EventListener;

use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class LocaleListener implements EventSubscriberInterface
{
    private $defaultLocale;

    public function __construct($defaultLocale = 'en')
    {
        $this->defaultLocale = $defaultLocale;
    }

    public function onKernelRequest(GetResponseEvent $event)
    {
        $request = $event->getRequest();
        if (!$request->hasPreviousSession()) {
            return;
        }

        // try to see if the locale has been set as a _locale routing parameter
        if ($locale = $request->attributes->get('_locale')) {
            $request->getSession()->set('_locale', $locale);
        } else {
            // if no explicit locale has been set on this request, use one from the session
            $request->setLocale($request->getSession()->get('_locale', $this->defaultLocale));
        }
    }

    public static function getSubscribedEvents()
    {
        return array(
            // must be registered before the default Locale listener
            KernelEvents::REQUEST => array(array('onKernelRequest', 17)),
        );
    }
}

Then register the listener:

• YAML

  services:
      app.locale_listener:
          class: AppBundle\EventListener\LocaleListener
          arguments: ["%kernel.default_locale%"]
          tags:
              - { name: kernel.event_subscriber }
  

• XML

  <service id="app.locale_listener"
      class="AppBundle\EventListener\LocaleListener">
      <argument>%kernel.default_locale%</argument>
  
      <tag name="kernel.event_subscriber" />
  </service>
  

• PHP

  use Symfony\Component\DependencyInjection\Definition;
  
  $container
      ->setDefinition('app.locale_listener', new Definition(
          'AppBundle\EventListener\LocaleListener',
          array('%kernel.default_locale%')
      ))
      ->addTag('kernel.event_subscriber')
  ;
  

That’s it! Now celebrate by changing the user’s locale and seeing that it’s sticky throughout the request. Remember, to get the user’s locale, always use the Request::getLocale method:

// from a controller...
use Symfony\Component\HttpFoundation\Request;

public function indexAction(Request $request)
{
    $locale = $request->getLocale();
}