Symfony\Component\DependencyInjection\ContainerBuilder::register PHP Method

    public function register($id, $class = null)
    {
        return $this->setDefinition($id, new Definition($class));
    }

 /**
  * {@inheritdoc}
  */
 public function load(array $config, ContainerBuilder $container)
 {
     // checker
     $container->register('bravesheep_active_link.checker', 'Bravesheep\\ActiveLinkBundle\\ActiveChecker')->addArgument(new Reference('kernel'))->addArgument(new Reference('request_stack'));
     // twig extension
     $container->register('bravesheep_active_link.twig', 'Bravesheep\\ActiveLinkBundle\\Twig\\BravesheepActiveLinkExtension')->addArgument(new Reference('bravesheep_active_link.checker'))->addTag('twig.extension');
 }