ปััญหา Mpdf ใน PHP 8 Fatal error: Uncaught Error: Class "Mpdf" not found

<?php

require_once __DIR__ . '/vendor/autoload.php';

$mpdf = new Mpdf();

$mpdf->WriteHTML('<h1>Hello world!</h1>');
$mpdf->Output();

<?php

require_once __DIR__ . '/vendor/autoload.php';

$mpdf = new \Mpdf\Mpdf();
$mpdf->WriteHTML('<h1>Hello world!</h1>');
$mpdf->Output();