Magento 2.x Bootstrapped class example

Playground2.php

<?php
//@see https://www.davidaaronyoung.com/m2-debugging-playground-continued/
//I should live in the root dir next to index.php
require __DIR__ . '/app/bootstrap.php';

/**
 * Class Playground2
 */
class Playground2 {

	/**
	 * @var \Magento\Framework\App\Bootstrap
	 */
	protected $bootstrap;

	/**
	 * @var \Magento\Framework\App\State
	 */
	protected $state;

	/**
	 * @var \Magento\Framework\App\ObjectManager
	 */
	protected $objManager;

	/**
	 * Playground constructor.
	 */
	public function __construct()
	{
		$this->_loadBootstrap();
		$this->_loadObjectManager();
		$this->_loadAppState();
		$this->_setAreaCode();
	}

	/**
	 * Bootstrap M2
	 */
	protected function _loadBootstrap()
	{
		$this->bootstrap = \Magento\Framework\App\Bootstrap::create( BP, $_SERVER );
	}

	/**
	 * Get the object manager so we can interact
	 * with classes and handle DI
	 */
	protected function _loadObjectManager()
	{
		$this->objManager = $this->bootstrap->getObjectManager();
	}

	/**
	 * Load the application state class
	 */
	protected function _loadAppState()
	{
		$this->state = $this->objManager->get( '\Magento\Framework\App\State' );
	}

	/**
	 * Set the proper area code
	 *
	 * AREA_GLOBAL
	 * AREA_FRONTEND
	 * AREA_ADMIN
	 * AREA_ADMINHTML
	 * AREA_DOC
	 * AREA_CRONTAB
	 * AREA_WEBAPI_REST
	 * AREA_WEBAPI_SOAP
	 */
	protected function _setAreaCode()
	{
		$this->state->setAreaCode( \Magento\Framework\App\Area::AREA_FRONTEND );
	}

	/**
	 * And an example debugging method
	 */
	public function echoCategoryName()
	{
		/** @var \Magento\Catalog\Model\Category $_categoryModel */
		$_categoryModel = $this->objManager->get( 'Magento\Catalog\Model\Category' );

		$_category = $_categoryModel->load( 1 );

		echo $_category->getName();
	}

}

$playground = new Playground2();

$playground->echoCategoryName();