title: Find maximum value in associative array
body: <p>I have a associative array:</p>
  
  <pre><code>$users[0] = array('name' =&gt; 'Jim', 'depth' =&gt; '1', 'bk_id' =&gt; '9'); 
  $users[1] = array('name' =&gt; 'Jill', 'depth' =&gt; '3', 'bk_id' =&gt; '10'); 
  $users[2] = array('name' =&gt; 'Jack', 'depth' =&gt; '7', 'bk_id' =&gt; '17'); 
  </code></pre>
  
  <p>I would like to know a way of finding the array index with the maximum or greatest depth value?</p>
  
  <p>Any suggestion is most appreciated.</p>