修复 导出csv中文乱码

     	header('Content-Encoding: UTF-8');
        header("Content-type: text/csv;charset=UTF-8");
        header("Content-Disposition: attachment; filename={$file_name}.csv");
        header("Pragma: no-cache");
        header("Expires: 0");
        $bom = chr(0xEF).chr(0xBB).chr(0xBF);
        exit($bom.$str);