title: getEntityManager() and getDoctrine() in Symfony2
body: <p>Is there any difference between these two statements: </p>
  
  <pre><code>$this-&gt;getDoctrine()-&gt;getEntityManager()-&gt;getRepository();
  
  $this-&gt;getDoctrine()-&gt;getRepository();
  </code></pre>
  
  <p>Does the difference relate to any OOP concept I am missing out? </p>