Change locales symfony 5.2

homepage.html.twig

{% set route = app.request.attributes.get('_route') %}
{% set route_params = app.request.attributes.get('_route_params') %}
{% set params = route_params|merge(app.request.query.all) %}

<a class="dropdown-toggle" href="#">
    <img src="{{ asset('build/media/images/flags/' ~ app.request.locale ~ '.png') }}" alt="{{ app.request.locale }}" />
</a>
<div class="dropdown">
    {% for locale in locales  %}
        <a class="dropdown-item" href="{{ path(route, params|merge({ _locale: locale })) }}">
            <img src="{{ asset('build/media/images/flags/' ~ locale ~ '.png') }}" alt="{{ locale }}" width="20" >
            <span>{{ locale }}</span>
        </a>
    {% endfor %}
</div>

LocaleStorage.php

<?php

namespace App\Core\Locale;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Session\SessionInterface;

class LocaleStorage
{
    const DEFAULT_LANGUAGE = 'fr';
    const FALLBACK_LANGUAGE = 'en';
    const LANGUAGES = [self::DEFAULT_LANGUAGE, self::FALLBACK_LANGUAGE];

    const SESSION_STORAGE_KEY = '_locale';

    /**
     * @var SessionInterface
     */
    private $session;

    /**
     * LocaleStorage constructor.
     *
     * @param SessionInterface $session
     */
    public function __construct(SessionInterface $session)
    {
        $this->session = $session;
    }

    /**
     * @return string
     */
    public function get()
    {
        return $this->session->get(static::SESSION_STORAGE_KEY, static::DEFAULT_LANGUAGE);
    }

    /**
     * @param string $locale
     */
    public function set(string $locale)
    {
        if (!\in_array($locale, static::LANGUAGES)) {
            $locale = static::FALLBACK_LANGUAGE;
        }

        $this->session->set(static::SESSION_STORAGE_KEY, $locale);
    }

    /**
     * @param Request $request
     */
    public function setFromPreferred(Request $request)
    {
        if ($this->session->has(static::SESSION_STORAGE_KEY)) {
            return;
        }

        $preferred = $request->getPreferredLanguage(static::LANGUAGES);
        $this->set($preferred);
    }
}

RequestLocaleListener.php

<?php

namespace App\Core\Locale;

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

class RequestLocaleListener implements EventSubscriberInterface
{
    /**
     * @var LocaleStorage
     */
    private $storage;

    /**
     * RequestLocaleListener constructor.
     *
     * @param LocaleStorage $storage
     */
    public function __construct(LocaleStorage $storage)
    {
        $this->storage = $storage;
    }

    /**
     * @param KernelEvent $event
     */
    public function onKernelRequest(KernelEvent $event)
    {
        $request = $event->getRequest();
        if (!$request->hasPreviousSession()) {
            return;
        }

        $locale = $request->attributes->get('_locale', $request->query->get('_locale'));
        if (null !== $locale) {
            $this->storage->set($locale);
            $request->setLocale($locale);

            return;
        }

        $this->storage->setFromPreferred($request);
        $request->setLocale($this->storage->get());
    }

    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents()
    {
        return [
            KernelEvents::REQUEST => [['onKernelRequest', 20]],
        ];
    }
}

translation.yaml

framework:
    default_locale: !php/const App\Core\Locale\LocaleStorage::DEFAULT_LANGUAGE
    translator:
        default_path: '%kernel.project_dir%/translations'
        fallbacks:
            - !php/const App\Core\Locale\LocaleStorage::FALLBACK_LANGUAGE

twig.yaml

twig:
    globals:
        locales: !php/const App\Core\Locale\LocaleStorage::LANGUAGES