function getTmpDir(): string
{
    $tmp = ini_get('upload_tmp_dir');
​
    if ($tmp !== False && file_exists($tmp)) {
        return realpath($tmp);
    }
​
    return realpath(sys_get_temp_dir());
}
​
$config = [
    'path' => getTmpDir() . '/',
];
​
$fileName   = 'tutorial01.xlsx';
$xlsxObject = new \Vtiful\Kernel\Excel($config);
​
// Init File
$fileObject = $xlsxObject->fileName($fileName);
​
// Writing data to a file ......
​
// Outptu
$filePath = $fileObject->output();
​
// Set Header
header("Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
header('Content-Disposition: attachment;filename="' . $fileName . '"');
header('Content-Length: ' . filesize($filePath));
header('Content-Transfer-Encoding: binary');
header('Cache-Control: must-revalidate');
header('Cache-Control: max-age=0');
header('Pragma: public');
​
ob_clean();
flush();
​
if (copy($filePath, 'php://output') === false) {
    // Throw exception
}
​
// Delete temporary file
@unlink($filePath);