A problem when export xlsx format

[seongmo]

I'm sorry for my bad english.

When I use export method with xlsx format, it downloaded xls extension.

So, I fix setHeaders method like this.

private function setHeaders()
    {
        // Set the headers
        switch($this->ext)
        {
            case 'xlsx':
                header('Content-type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
                break;

            case 'csv':
                header('Content-type: application/csv');
                break;

            default: // xls
                header('Content-Type: application/vnd.ms-excel');
                break;
        }


        header('Content-Disposition: attachment;filename="' . $this->title . '.'. $this->ext .'"');
        header('Cache-Control: max-age=0');
        header('Cache-Control: max-age=1');
        header('Expires: Mon, 26 Jul 1997 05:00:00 GMT'); // Date in the past
        header('Last-Modified: '.gmdate('D, d M Y H:i:s').' GMT'); // always modified
        header('Cache-Control: cache, must-revalidate'); // HTTP/1.1
        header('Pragma: public'); // HTTP/1.0
    }