Create a culture switch in Symfony2

LocaleListener.php

<?php

namespace Your\Bundle\Listener;

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;
        }

        if ($locale = $request->attributes->get('_locale')) {
            $request->getSession()->set('_locale', $locale);
        } else {
            $request->setLocale($request->getSession()->get('_locale', $this->defaultLocale));
        }
    }

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

service.xml

<service id="my.listener" class="Your\Bundle\Listener\LocaleListener">
    <argument>%locale%</argument>
    <tag name="kernel.event_subscriber"/>
</service>

view.html.twig

{% for locale in ['en', 'fr','zh'] %}
    <li>
      <a href="{{ path(app.request.get('_route'), app.request.get('_route_params')|merge({'_locale' : locale})) }}">
        {% if locale == 'en' %}
            <img title="English" src="{{ asset('bundles/fkmywebsite/images/UnitedStates.png') }}" alt="English" height="30" width="30"/>
        {% elseif locale == 'fr' %}
            <img title="Français" src="{{ asset('bundles/fkmywebsite/images/France.png') }}" alt="Français" height="30" width="30"/>
        {% endif %}
      </div>
    </li>
{% endfor %}