In case you haven't come to a conclusion... I took Henrique's answer and gave a better logic solution. This is completely compatible with PHPSpreadSheet in case someone is using PHPSpreadSheet or PHPExcel.
$spreadOrPhpExcel = new SpreadSheet(); // or new PHPExcel();
print_in_sheet($spreadOrPhpExcel);
function print_in_sheet($spread)
{
$sheet = 0;
foreach( getData() as $report => $value ){
# If number of sheet is 0 then no new worksheets are created
if( $sheet > 0 ){
$spread->createSheet();
}
# Index for the worksheet is setted and a title is assigned
$wSheet = $spread->setActiveSheetIndex($sheet)->setTitle($report);
# Printing data
$wSheet->setCellValue("A1", "Hello World!");
# Index number is incremented for the next worksheet
$sheet++;
}
return $spread;
}