How to work with sessions in Silex (Symfony)

My objective is to learn how to work with sessions in Silex 1.2 / Symfony.

First step is to create a session with Session(). I want to store it into $app['session'].
Second step is to access the data stored into session variable.
Last step is to destroy session with invalidate() function.

However, when I do: var_dump($app['session']->get('user')); I get this error:

Identifier "session" is not defined

How can I access at $app['session'] from anywhere in my project ?

Routing and Controllers

// create session
$routes->get('/test1', function () use ($app) {
    $app['session'] = new Symfony\Component\HttpFoundation\Session\Session();
    $app['session']->start();
    $app['session']->set('user', 'test');

    return $app['twig']->render('test1.html.twig');
})
->bind('test1');

// try to access on session data
$routes->get('/test2', function () use ($app){
    var_dump($app['session']->get('user'));

    return $app['twig']->render('test2.html.twig');
})
->bind('test2');

// remove session
$routes->get('/test3', function () use ($app){
    $app['session']->invalidate();

    return $app['twig']->render('test3.html.twig');
})
->bind('test3');

Solution

You're only defining the session service in your first route. Any others don't have any idea about that identifier, so can't operate on it at all. Session data itself is persistent across requests, but not the actual creation of the service.

The lines

$app['session'] = new Symfony\Component\HttpFoundation\Session\Session();
$app['session']->start();

need to be moved outside of any route-specific configuration (usually into a configuration file such as src/app.php, although your structure might be different).

$app['session'] will then be available to use in any of your routes/controller methods/etc.

You might also want to look into using the SessionServiceProvider class instead, which will take care of registering this service and provide other useful benefits like saving the session at the end of the request/response cycle. See https://silex.symfony.com/doc/1.3/providers/session.html