php下载doc乱码怎么办

$file_size = filesize($logName);
        ob_end_clean();
        header("Content-type:application/octet-stream");
        header("Accept-Ranges:bytes");
        header("Accept-Length:$file_size");
        header("Content-Disposition:attachment;filename=" . $fileName);
        $fp = fopen($logName, "r");
        $buffer_size = 1024;
        $cur_pos = 0;
        while (!feof($fp) && $file_size - $cur_pos > $buffer_size) {
            $buffer = fread($fp, $buffer_size);
            echo$buffer;
            $cur_pos+=$buffer_size;
        }
        $buffer = fread($fp, $file_size - $cur_pos);
        echo$buffer;
        fclose($fp);
        return true;