title: Sort an assoc array index into reverse order
body: <p>Hey guys I hope a very quick one!</p>
  
  <p>I have an array </p>
  
  <pre><code>array(
  (int) 30 =&gt; array(
      'score' =&gt; (int) 30,
      'max_score' =&gt; (int) 40,
      'username' =&gt; 'joeappleton',
      'user_id' =&gt; '1'
  ),
  (int) 34 =&gt; array(
      'score' =&gt; (int) 34,
      'max_score' =&gt; (int) 40,
      'username' =&gt; 'joeappleton',
      'user_id' =&gt; '1'
  ),
  (int) 36 =&gt; array(
      'score' =&gt; (int) 36,
      'max_score' =&gt; (int) 40,
      'username' =&gt; 'joeappleton',
      'user_id' =&gt; '1'
  )
  </code></pre>
  
  <p>)</p>
  
  <p>I need it to be sorted into descending order, by reference of the array key:</p>
  
  <pre><code>array( 
      36 =&gt; array('score' =&gt; 36, 'max_score' =&gt; 40, 'username' =&gt; 'joeappleton', 'user_id' =&gt; '1'),
      34 =&gt; array('score' =&gt; 34, 'max_score' =&gt; 40, 'username' =&gt; 'joeappleton', 'user_id' =&gt; '1'),
      30 =&gt; array('score' =&gt; 36, 'max_score' =&gt; 40, 'username' =&gt; 'joeappleton', 'user_id' =&gt; '1')
  );
  </code></pre>
  
  <p>I've tried krsort() but no joy, it seems to return a bool. Any ideas? </p>