bootstrap.php

<?php

require_once __DIR__ . '/silex.phar';

require_once 'phar://' . __DIR__ . '/silex.phar/vendor/Symfony/Component/ClassLoader/UniversalClassLoader.php';

use Symfony\Component\ClassLoader\UniversalClassLoader;

$loader = new UniversalClassLoader();
$loader->register();

/**
 * @desc Add local pear setup.
 */
set_include_path(__DIR__ . '/vendor/pear:' . get_include_path());

$app = new Silex\Application();

// register twig for views
$app->register(new Silex\Extension\TwigExtension(), array(
    'twig.path'       => __DIR__ . '/views',
    'twig.class_path' => __DIR__ . '/vendor/fabpot-Twig-612fa7b/lib/',
));

// load session extensions
$app->register(new Silex\Extension\SessionExtension());


$app['session.storage'] = new Symfony\Component\HttpFoundation\SessionStorage();
// class not found error

var_dump($app['session']); exit;