insertFormula(int $row, int $column, string $formula [, resource $formatHandler])
$excel = new \Vtiful\Kernel\Excel($config);
$freeFile = $excel->fileName("free.xlsx")
->header(['name', 'money']);
for($index = 1; $index < 10; $index++) {
$freeFile->insertText($index, 0, 'viest');
$freeFile->insertText($index, 1, 10);
}
$freeFile->insertText(12, 0, "Total");
$freeFile->insertFormula(12, 1, '=SUM(B2:B11)');
$freeFile->output();