How to Locked Excel cell in PHP Spreadsheet

<?php
require 'vendor/autoload.php';
use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;
$spreadsheet = new Spreadsheet();
$sheet = $spreadsheet->getActiveSheet();
$sheet->setCellValue('A1', 'Hello World !');
$sheet->setCellValue('B1', 'Divyasundar Sahu !');
$sheet->getProtection()->setSheet(true);
$writer = new Xlsx($spreadsheet);
$writer->save('hello world.xlsx');
?>