title: Laravel 5 - ORM has() Relationship (Inverse - notHas)
body: <p>In the Laravel 5 I can find all posts that have at least one comment using <code>has</code> method:</p>
  
  <pre><code>// Retrieve all posts that have at least one comment...
  $posts = App\Post::has('comments')-&gt;get();
  </code></pre>
  
  <p>As theres no method like <code>notHas</code>, how can I find all posts that have no comments? 
  (remembering that it's a <code>hasMany</code> relationship)</p>
  
  <hr>
  
  <p><em>Reference:</em></p>
  
  <p><strong>Querying Relationship Existence</strong></p>
  
  <p><a href="http://laravel.com/docs/5.1/eloquent-relationships#querying-relations" rel="noreferrer">http://laravel.com/docs/5.1/eloquent-relationships#querying-relations</a></p>