Under app/config/config.yml I have an entry for:

  parameters:
    bar: "yes"

If I attempt to access this parameter through a controller (under dev environment aka app_dev.php):

class DefaultController extends Controller
{
    public function indexAction()
    {
        var_dump($this->container->parameters['bar']);die;
    }
}

the value "yes" is dumped out.

When I access this under prod environment, it returns null. I'm not sure why as this parameter was defined in config.yml which is used by prod and dev (config.yml is imported into config_dev.yml).

If I switch the order around, everything works as expected. Basically, if I go to app.php first, the correct value is returned. If I then go to app_dev.php the correct value is returned. It seems to me that there is some sort of cache issue going on.