Why are curly brackets missing from formulas when saving a file in phpexel?

Question

PHP

I do it this way, I created a template, the first sheet is empty, a price is generated in it, in the remaining two sheets of the formula, for an array in exel I press ctrl + shift + enter {}
After the price is generated, the formulas disappear {}

require_once($_SERVER["DOCUMENT_ROOT"].'/upload/documents/Classes/PHPExcel.php');
require_once($_SERVER["DOCUMENT_ROOT"].'/upload/documents/Classes/PHPExcel/IOFactory.php');


$fileType = 'Excel2007';
$fileName = 'empty2.xlsx';

// Read the file
$objReader = PHPExcel_IOFactory::createReader($fileType);
$objPHPExcel = $objReader->load($fileName);



// Write the file
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, $fileType);
$objWriter->save('testFile2.xlsx');