public function insertAfter($value, $afterKey)
    {
        $new_object = new self();

        foreach ((array)$this->items as $k => $v) {
            if ($afterKey == $k) {
                $new_object->add($value);
            }

            $new_object->add($v);
        }

        $this->items = $new_object->items;

        return $this;
    }