// 文件下载
    private function download ($filename, $showname='',$content='',$expire=180) {  
		if(file_exists($filename)){  
			$length = filesize($filename);  
		}elseif(is_file(UPLOAD_PATH.$filename)){  
			$filename = UPLOAD_PATH.$filename;  
			$length = filesize($filename);  
		}elseif($content != ''){  
			$length = strlen($content);   
		}else {  
			throw_exception($filename.L('下载文件不存在！'));  
		}  
		if(empty($showname)){  
			$showname = $filename;  
		}  
		$showname = basename($showname);  
		if(empty($filename)){  
			$type = mime_content_type($filename);  
		}else{  
			$type = "application/octet-stream";  
		}  
		//发送Http Header信息 开始下载  
		header("content-type:text/html; charset=utf-8");  
		header("Pragma: public");  
		header("Cache-control: max-age=".$expire);  
		//header('Cache-Control: no-store, no-cache, must-revalidate');  
		header("Expires: " . gmdate("D, d M Y H:i:s",time()+$expire) . "GMT");  
		header("Last-Modified: " . gmdate("D, d M Y H:i:s",time()) . "GMT");  
		//下面一行就是改动的地方，即用iconv("UTF-8","GB2312//TRANSLIT",$showname)系统函数转换编码为gb2312  
		header("Content-Disposition: attachment; filename=". iconv("UTF-8","GB2312",$showname)); header("Content-Length: ".$length);  
		header("Content-type: ".$type);  
		header('Content-Encoding: none');  
		header("Content-Transfer-Encoding: binary" );  
		if($content == '' ) {  
			readfile($filename);  
		}  
		else { echo($content); }  
		exit();    
}