This is the simple silex app.

app.php

<?php

require_once dirname(__DIR__) . '/vendor/autoload.php';

use Silex\Application;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$app = new Silex\Application();

$app['debug'] = true;

$app->register(new Silex\Provider\SecurityServiceProvider());
$app->register(new Silex\Provider\SessionServiceProvider());
$app->register(new Silex\Provider\TwigServiceProvider(), array(
    'twig.path' => dirname(__DIR__) . '/src/views'
));
$app->register(new Silex\Provider\UrlGeneratorServiceProvider());

$app['security.firewalls'] = array(
    'admin' => array(
        'pattern' => '^/admin/?',
        'form'    => array('login_path' => '/login', 'check_path' => '/admin/login_check'),
        'logout'  => array('logout_path' => '/logout'),
        'users'   => array(
            'admin' => array('ROLE_ADMIN', '5FZ2Z8QIkA7UTZ4BYkoC+GsReLf569mSKDsfods6LYQ8t+a8EW9oaircfMpmaLbPBh4FOBiiFyLfuZmTSUwzZg=='),
        ),
    ),
);

$app->get('/', function(Request $request) use ($app) {
    return new Response('index', 200);
});

$app->get('/admin', function(Request $request) use ($app) {
    return new Response('admin', 200);
});

$app->get('/logout', function() use ($app) {
    return new Response('logout', 200);
});

$app->get('/login', function(Request $request) use ($app) {
    return $app['twig']->render('login.twig', array(
        'error'         => $app['security.last_error']($request),
        'last_username' => $app['session']->get('_security.last_username'),
    ));
});

$app->run();