public function isDie() {
        if ($this->_time > 0) {
            $die = false;

            if (!file_exists($this->_fileName)) {
                $die = true;
            }
            else {
                $timeAgo = time() - filemtime($this->_fileName);
                if ($timeAgo > $this->_time) {
                    $die = true;
                }
            }

            return $die;
        }
        else {
            return true;
        }
    }