AppKernel.php

<?php

    // app/AppKernel.php

    public function registerContainerConfiguration(LoaderInterface $loader)
    {
        $envParameters = $this->getEnvParameters();
        if (@$envParameters['domain.name'] == 'domain2') {
            $loader->load(__DIR__.'/config/domain2/config_'.$this->getEnvironment().'.yml');
        } else {
            $loader->load(__DIR__.'/config/config_'.$this->getEnvironment().'.yml');
        }
    }

    public function getCacheDir()
    {
        $envParameters = $this->getEnvParameters();
        if (@$envParameters['domain.name'] == 'domain2') {
            $cacheDir = $this->rootDir.'/cache/domain2/'.$this->environment;
        } else {
            $cacheDir = $this->rootDir.'/cache/'.$this->environment;
        }

        return $cacheDir;
    }