public function download($currdir = null){

     $file = urldecode($currdir);

     $file = iconv('UTF-8', "GB2312", $file);

     if (!file_exists($file)) {

         $this->error("文件不存在");

     }

     //basenamecn 是common文件自定义的方法

     $filename = basenamecn(iconv('GB2312', "UTF-8", $file));

     //告诉浏览器以附件处理

     header('Content-Disposition: attachment;filename=' . $filename);

     readfile($file);

 }