protected function sort($data)
    {
        if (is_string($this->sort)) {
            $p = $this->sort;
            usort($data, function ($a, $b) use ($p) {
                if ($a[$p] == $b[$p]) {
                    return 0;
                }
                return $a[$p] < $b[$p] ? -1 : 1;
            });
        } elseif ($this->sort === true) {
            sort($data);
        }
        return $data;
    }