AppKernel.php

<?php

use Symfony\Component\DependencyInjection\ContainerBuilder;

use Symfony\Component\HttpKernel\Kernel;
use Symfony\Component\Config\Loader\LoaderInterface;

class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            new \Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
            new \Symfony\Bundle\TwigBundle\TwigBundle(),
            new \Sensio\Bundle\FrameworkExtraBundle\SensioFrameworkExtraBundle(),
            new \AppBundle\AppBundle(),
            new \Symfony\Bundle\MonologBundle\MonologBundle(),
        );

        if ($this->getEnvironment() == 'dev') {
            $bundles[] = new \Symfony\Bundle\WebProfilerBundle\WebProfilerBundle();
            $bundles[] = new \Symfony\Bundle\DebugBundle\DebugBundle();
        }

        return $bundles;
    }

    public function registerContainerConfiguration(LoaderInterface $loader)
    {
        $loader->load(__DIR__.'/config/config.yml');
        $isDevEnv = $this->getEnvironment() == 'dev';

        // do some dynamic customizations
        $loader->load(function (ContainerBuilder $container) use($isDevEnv) {
            if($isDevEnv) {
                $container->loadFromExtension('web_profiler', [
                    'toolbar' => true,
                ]);
            }
            if ($isDevEnv) {
                $container->loadFromExtension('framework', array(
                    'router' => array(
                        'resource' => '%kernel.root_dir%/config/routing_dev.yml',
                    )
                ));
            }
        });
    }
}