public function sortByKey($order = self::SORT_ASC, $type = self::SORT_REGULAR, $caseSensitive = true)
    {
        if ($caseSensitive === false) {
            $type = $type + SORT_FLAG_CASE;
        }
        if ($this->isAssociative() === true) {
            array_multisort(array_keys($this->arrayVar), $order, $type, $this->arrayVar);
        } else {
            if ($order == self::SORT_ASC) {
                ksort($this->arrayVar, $type);
            } else {
                krsort($this->arrayVar, $type);
            }
        }
        return $this;
    }