//下載指定檔案的方法
	public function downdetails($file_path){
		header("Content-type:text/html;charset=utf-8"); 
		//$file_path="testMe.txt";
		//用以解決中文不能顯示出來的問題 
		//$file_name=iconv("utf-8","gb2312",$file_name);
		//$file_sub_path=$_SERVER['DOCUMENT_ROOT']."marcofly/phpstudy/down/down/"; 
		//$file_path=$file_sub_path.$file_name; 
		//首先要判斷給定的檔案存在與否 
		if(!file_exists($file_path)){
			echo "沒有該檔案檔案"; 
			return ; 
		}
		$fp=fopen($file_path,"r");
		$file_size=filesize($file_path);
		//下載檔案需要用到的頭
		Header("Content-type: application/octet-stream");
		Header("Accept-Ranges: bytes"); 
		Header("Accept-Length:".$file_size); 
		Header("Content-Disposition: attachment; filename=".$file_path); 
		$buffer=1024; 
		$file_count=0; 
		//向瀏覽器返回資料 
		while(!feof($fp) && $file_count<$file_size){ 
			$file_con=fread($fp,$buffer); 
			$file_count+=$buffer; 
			echo $file_con; 
		}
		fclose($fp);
	}