Twig_NodeVisitorInterface::enterNode PHP Method

    public function enterNode(Twig_NodeInterface $node, Twig_Environment $env);

 private function traverseForVisitor(Twig_NodeVisitorInterface $visitor, Twig_Node $node)
 {
     $node = $visitor->enterNode($node, $this->env);
     foreach ($node as $k => $n) {
         if (false !== ($n = $this->traverseForVisitor($visitor, $n))) {
             $node->setNode($k, $n);
         } else {
             $node->removeNode($k);
         }
     }
     return $visitor->leaveNode($node, $this->env);
 }