Crear Excel con Spreadsheet

composer require phpoffice/phpspreadsheet
use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

$spreadsheet = new Spreadsheet();
$sheet = $spreadsheet->getActiveSheet();

$sheet->getStyle('A1:D1')->getFill()
->setFillType(\PhpOffice\PhpSpreadsheet\Style\Fill::FILL_SOLID)
->getStartColor()
->setARGB('702082');

$sheet->getStyle('A1:D1')->getFont()->setColor( new \PhpOffice\PhpSpreadsheet\Style\Color( \PhpOffice\PhpSpreadsheet\Style\Color::COLOR_WHITE));
$sheet->getStyle('A1:D1')->getFont()->setSize(14);

$sheet->getColumnDimension('A')->setAutoSize(true);
$sheet->getColumnDimension('B')->setAutoSize(true);
$sheet->getColumnDimension('C')->setAutoSize(true);
$sheet->getColumnDimension('D')->setAutoSize(true);

$sheet->setCellValue('A1', 'xxx');
$sheet->setCellValue('B1', 'xxx');
$sheet->setCellValue('C1', 'xxx');
$sheet->setCellValue('D1', 'xxx');

$contFila = 1;

foreach ($resultExcel as $item) {
$contFila++;
$sheet->setCellValue('A'.$contFila, $item->xxx);
$sheet->setCellValue('B'.$contFila, $item->xxx);
$sheet->setCellValue('C'.$contFila, $item->xxx);
$sheet->setCellValue('D'.$contFila, $item->xxx);
}

$writer = new Xlsx($spreadsheet);
// $writer->save('hello world.xlsx');
header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
header('Content-Disposition: attachment; filename="loquesea.xlsx"');
$writer->save('php://output'); // para q se descargue en vez de guardar