switch($_FILES[$field]['error']) {       case 1:            // 文件大小超出了服务器的空间大小            $this->setError("The file is too large (server).");    break;    case 2:            // 要上传的文件大小超出浏览器限制            $this->setError("The file is too large (form).");            break;        case 3:            // 文件仅部分被上传            $this->setError("The file was only partially uploaded.");            break;        case 4:            // 没有找到要上传的文件            $this->setError("No file was uploaded.");            break;        case 5:            // 服务器临时文件夹丢失            $this->setError("The servers temporary folder is missing.");            break;        case 6:            // 文件写入到临时文件夹出错            $this->setError("Failed to write to the temporary folder.");            break;    }