I'm facing an issue while exporting Excel using PHP Spreadsheet and CodeIgniter 3 in PHP 8.2. The error message is shown in the following image:
Here is the code snippet that I'm using:
$fileName = 'activityReport.xlsx';
$this->load->library('ciSpreadsheet');
$spreadsheet = new Spreadsheet();
$spreadsheet->getProperties()->setCreator("CalibOn")
->setLastModifiedBy("CalibOn")
->setTitle("Activity Report")
->setSubject("Activity Report")
->setDescription("Activity Report")
->setKeywords("")
->setCategory("Report");
$spreadsheet->setActiveSheetIndex(0);
$col_array = array('Activity Date', 'Activity Time', 'Account Name', 'Activity Type', 'Contacted', 'Outcome', 'Description', 'Activity By', 'Created Date', 'Created Time');
$col_array_key = array('ActivityDate', 'ActivityTime', 'AccountName', 'ActivityType', 'Contacted', 'Outcome', 'Description', 'ActivityBy', 'CreatedDate', 'CreatedTime');
$col_count = 1;
$row_count = 1;
$sheet = $spreadsheet->getActiveSheet();
foreach ($col_array as $value) {
$sheet->setCellValue($this->getNameFromNumber($col_count) . $row_count, $value);
$col_count++;
}
$row_count++;
foreach ($report_array as $key => $value) {
$col_count = 1;
foreach ($col_array_key as $key_c => $value_col) {
$sheet->setCellValue($this->getNameFromNumber($col_count) . $row_count, $value->$value_col);
$col_count++;
}
$row_count++;
}
header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="' . $fileName . '"');
header('Cache-Control: max-age=0');
$writer = IOFactory::createWriter($spreadsheet, 'Xlsx');
$writer->save("php://output");
exit;
The reportData variable, which is fetched from the database, follows the sample format below:
Array(
[0] => Array(
[ActivityDate] => 2022-06-28,
[ActivityTime] => 14:00:00,
[AccountName] => "Name",
[ActivityType] => "Visit",
[Description] => "desc",
[Contacted] => "completed by",
[Outcome] => ,
[ActivityBy] => "generated by",
[CreatedDate] => 2022-07-08,
[CreatedTime] => 17:13:59
)
);
I'm seeking assistance to resolve the error and successfully export the Excel file. Any guidance or suggestions on fixing the issue would be highly appreciated.

Please use this after writer initialization.
Also,Change the header content type to the below given snippet