title: What means Call to a member function on boolean and how to fix
body: <p>I'm new with cakePHP 3. I have created a controller and model where I call a function to get all users from the database. 
  But when I run the code below I will get the following error <em>"Call to a member function get_all_users() on boolean"</em>. </p>
  
  <p>what does this error means and how can I fix this up?</p>
  
  <p><strong>User.php (model)</strong></p>
  
  <pre><code>namespace App\Model\Entity;
  use Cake\ORM\Entity;
  
  class User extends Entity {
  
      public function get_all_users() {
          // find users and return to controller
          return $this-&gt;User-&gt;find('all');
      }
  }
  </code></pre>
  
  <p><strong>UsersController.php (controller)</strong></p>
  
  <pre><code>namespace App\Controller;
  use App\Controller\AppController;
  
  class UsersController extends AppController {
  
      public function index() {
          // get all users from model
          $this-&gt;set('users', $this-&gt;User-&gt;get_all_users());
      }
  }
  </code></pre>