The plus sign is deleted when importing to the xls file

Laravel version 5.4

Expected behaviour

Actual behaviour

Steps to reproduce the behaviour

$sheet->setColumnFormat(array(
                    'A' => '@'
                ));
                foreach ($order_details as $key => $detail) {
                 $sheet->appendRow([(string)$detail->model->id_supplier, $detail->model->mintitle, $detail->qty, $detail->price, $detail->qty * $detail->price,]);
                 $sheet->setHeight($sheet->getHighestRow(), 45);
                }

How to import a number with a plus sign?

via Chebli Mohamed