Drupal 8 Controller Example

ExampleController.php

<?php

/**
 * @file
 * Contains \Drupal\session_test\Controller\ExampleController.
 */

namespace Drupal\example\Controller;

use Drupal\Core\ControllerInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Config\ConfigFactory;

/* All global variables here. */
use Symfony\Component\HttpFoundation\Request;

/**
 * Provides page callbacks for the configuration interface.
 */
class ExampleController implements ControllerInterface {
  /**
   * Stores the configuration factory.
   *
   * @var \Drupal\Core\Config\ConfigFactory
   */
  protected $configFactory;

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('config.factory'));
  }

  /**
   * Constructs a object.
   */
  public function __construct(ConfigFactory $config_factory) {
    $this->configFactory = $config_factory;
  }
  
  /* @see: https://drupal.org/node/2032447 */
  public function getGlobalUser() {
    return Drupal::currentUser();
  }
  
  public function getGlobalCookie(Request $request) {
    return $request->cookies->get(session_name());
  }
  
  public function getSession($key, Request $request) {
    return $request->getSession()->get($key);
  }
  
  public function setSession($key, $value, Request $request) {
    $session = $request->getSession();
    $session->set($key, $value);
    $request->setSession($session);
  }
}