Symfony2 multiple kernels

app_config.yml

# frontend specific config in /frontend/config/config.yml
imports:
    - { resource: security.yml }

...

AppKernel.php

<?php

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

// base kernel in app/AppKernel.php
class AppKernel extends Kernel
{

    public function registerBundles()
    {
        $bundles = array(
            new Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
            // ...
        );

        return $bundles;
    }


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

frontend_config.yml

# common configuration in app/config/config.yml 

imports:
    - { resource: redis.yml }
    - { resource: parameters.yml }

... 

FrontendKernel.php

<?php
require __DIR__ .'/../app/AppKernel.php';

use Symfony\Component\Config\Loader\LoaderInterface;

// frontend specific kernel in frontend/FrontendKernel.php
class FrontendKernel extends \AppKernel
{
    /**
     * {@inheritDoc}
     */
    public function registerBundles()
    {
        $bundles = parent::registerBundles();
        $bundles[] = new FOS\JsRoutingBundle\FOSJsRoutingBundle();
        return $bundles;
    }

    public function registerContainerConfiguration(LoaderInterface $loader)
    {
        // load parent config
        parent::registerContainerConfiguration($loader);
        // load child-kernel config
        $loader->load(__DIR__.'/config_'.$this->getEnvironment().'.yml');
    }
}