Drupal minimal bootstrap.

test.php

<?php

/**
 * @file
 * Drupal minimal bootstrap.
 */

use Drupal\Core\DrupalKernel;
use Symfony\Component\HttpFoundation\Request;

$autoloader = require_once 'autoload.php';

$kernel = DrupalKernel::createFromRequest(Request::createFromGlobals(), $autoloader, 'prod');
$kernel->loadLegacyIncludes();
$kernel->boot();
// Drupal code here.

<?php
// test.php
/**
 * @file
 * Drupal full bootstrap with modules.
 */
use Drupal\Core\DrupalKernel;
use Symfony\Component\HttpFoundation\Request;
$autoloader = require_once 'autoload.php';
$request = Request::createFromGlobals();
$kernel = DrupalKernel::createFromRequest($request, $autoloader, 'prod', TRUE, __DIR__);
$kernel->boot();
$kernel->preHandle($request);