Admin Users

An application can test whether the currently signed-in user is a registered administrator for the application. An administrator is a user who can access the Administration Console for the application. You can use the Administration Console to manage which users have administrator status.

The function UserService::isCurrentUserAdmin() returns True if the current user is an administrator for the application.

appengine/php55/users/app.php 
use google\appengine\api\users\User;
$user = UserService::getCurrentUser();
if (isset($user) && UserService::isCurrentUserAdmin()) {
    return 'Welcome administrator.';
}
return 'You are not an administrator.';

Tip: An easy way to restrict access to a part of your application to administrators is to use the login: admin configuration element for the URL handler. See Configuring an App.