How to initialize or bootstrap Drupal in a standalone PHP script

I found this today while searching the web exactly for how to do that, but the answer wasn't very easy to find.

https://hibern8.wordpress.com/2018/09/25/drupal-8-bootstrap-from-external-script/

Reproducing here in case the site goes offline.

As this code is from 2018, it should work with Drupal 8, maybe Drupal 8.9, and hopefully with Drupal 9 and 10. I will test when I have time.

Bootstrap Drupal 8 from external script

Posted on September 25, 2018 by hibern8

Today i was trying to access my Drupal 8 site from an external php script, i ended up with this code:

<?php
namespace Drupal\Core;

define('DRUPAL_DIR', '/var/www/drupal8');
define('DRUPAL_SITE', 'default');

$autoloader = require_once DRUPAL_DIR.'/autoload.php';

use Drupal\Core\Site\Settings;
use Drupal\Core\DrupalCliKernel;

class DrupalCliKernel extends DrupalKernel {

  public function bootstrap() {
    static::bootEnvironment();
    $this->setSitePath('sites/'.DRUPAL_SITE);
    Settings::initialize($this->root, 'sites/'.DRUPAL_SITE, $this->classLoader);
    $this->boot();
  }
}

$kernel = new DrupalCliKernel('prod', $autoloader);
$kernel->bootstrap();

// Drupal is bootstrapped now.