$is_https global removed

Before D8 $is_https global, was defined in early bootstrap process of drupal depending on whether the request was under a secure enviroment (HTTPS) or not.

As of Drupal 8 this global no longer exists since Symfony's Request::isSecure() method duplicates this functionality.

D7

global $is_https;

if ($is_https) {
  // Do stuff..
}

D8

// In class context with Request object injected:
if ($this->request->isSecure()) {
  // Do stuff..
}

// If request is not available as an injected object
if (Drupal::request()->isSecure()) {
  // Do stuff..
}