Using boot() to add global variables in Twig

gistfile1.aw

<?php

namespace My\BackendBundle;

use Symfony\Component\HttpKernel\Bundle\Bundle;

class BackendBundle extends Bundle
{
    public function boot()
    {
        $twig = $this->container->get('twig');

        $twig->addGlobal('backend', array(
            'title' => $this->container->getParameter('backend.title')
        ));
    }
}