public function flush()
    {
        $list = glob($this->filePath . '*');
        foreach ($list as $file) {
            unlink($file);
        }
        return true;
    }
public function flush()
    {
        $list = glob($this->filePath . '*');
        foreach ($list as $file) {
            unlink($file);
        }
        return true;
    }
清空所有缓存
@return mixed