Uncaught Error: Call to undefined function Spatie\Sitemap\app()

[zerocarbthirty]

Hi, just setting this project up on a server to generate sitemaps:

<?php
require __DIR__ . '/vendor/autoload.php';
use Spatie\Sitemap\SitemapGenerator;
$path = "sitemap.xml";
SitemapGenerator::create('https://thewebsite.com')->writeToFile($path);

Does this code have to be ran from inside of a Laravel project?

I'm not really sure what app() is supposed to be.

I installed it with require spatie/laravel-sitemap

I assume if it required ALL of Laravel it would've installed Laravel?