Symfony2: how to log user out manually in controller?

In Symfony 4/5 this is just enough to remove user:

    /**
     * @var TokenStorageInterface $token_storage
     */
    private TokenStorageInterface $token_storage;

    /**
     * Will force logout from system
     */
    public function logoutCurrentlyLoggedInUser()
    {
        $this->token_storage->setToken(null);
    }

Now You can create a method to use it later to check if user is logged in:

class Application extends AbstractController {...

    /**
     * Returns currently logged in user
     * @return object|UserInterface|null
     */
    public function getCurrentlyLoggedInUser()
    {
        return $this->getUser();
    }

In case you are using symfony 4.x (I haven't tested other versions, so it still might work), you may want to use the internal logout handler of symfony (highly recommended, as it will take care of everything for you in a clean way, cookies and all). You don't need to write too much code for that either, you can simply emulate a logout request:

... // Some code, that leads you to force logout the user 
// Emulating logout request
$logoutPath = $this->container->get('router')->generate('app_logout');
$logoutRequest = Request::create($logoutPath);
$logoutResponse = $this->container->get('http_kernel')->handle($logoutRequest);
// User is logged out now
... // Stuff to do after logging out, eg returning response

This will make symfony do the request response flow, thus it will call the logout handler internally. This method allows you to proceed to further custom code. Otherwise, if you invoked only the logout listener here, you would have to return the usual logout response, that now is in $logoutResponse. Optionally, if you want to return it, you would also simply:

return $logoutResponse;

The proposed solutions didn't work for me in Symfony 5.3. It should be something as basic as

session_start();
session_destroy();

So I did this way:

$this->get('session')->start();
$this->get('session')->invalidate();

This will terminate the PHP Session, which is the way most of sessions work in Symfony.