public function insertNode($new_node, $existing_node, $before = false)
    {
        $pos = 0;
        $exist_pos = $existing_node->getPosition();
        $this->rewind();

        // Now add the node according to the requested mode
        switch ($before) {

        case true:
            $this->add($exist_pos, $new_node);
            break;

        // after
        case false:
            if ($this->offsetExists($exist_pos + 1)) {
                $this->add($exist_pos + 1, $new_node);
            } else {
                $this->appendNode($new_node);
                return true;
            }
            break;
        }

        // Fix positions
        $this->rewind();
        while ($n = $this->current()) {
            $n->setPosition($pos);
            $this->next();
            $pos++;
        }

        return true;
    }