private function addPhpFileNode()
    {
        $builder = new TreeBuilder('php_file');
        $node    = $this->getRootNode($builder, 'php_file');

        $node
            ->addDefaultsIfNotSet()
            ->children()
                ->scalarNode('directory')->defaultValue('%kernel.cache_dir%/doctrine/cache/phpfile')->end()
                ->scalarNode('extension')->defaultNull()->end()
                ->integerNode('umask')->defaultValue(0002)->end()
            ->end()
        ;

        return $node;
    }