PhpSpreadsheet: Fatal error while using Writer\xlsx

Hi I have an error, help me please… What is the problem please ?

What is the expected behavior?

I want to create a XLSX file

Code ?

<?php
require 'phptoexcel/vendor/autoload.php';

use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

$spreadsheet = new Spreadsheet();
$sheet = $spreadsheet->getActiveSheet();
$sheet->setCellValue('A1', 'Hello World !');

$writer = new Xlsx($spreadsheet);
$writer->save('hello world.xlsx');

What is the current behavior?

There is fatal error : ( ! ) Fatal error: Class ‘PhpOffice\PhpSpreadsheet\Writer\Xlsx’ not found in C:\wamp64\www\timax\test.php on line 12

Which versions of PhpSpreadsheet and PHP are affected?

Last version with PHP 7