title: Get key of the last element in an array
body: <p>Hay, i have an array which contains a set of arrays, here's an example.</p>
  
  <pre><code>array(
      [0]=&gt;array('name'=&gt;'bob'),
      [2]=&gt;array('name'=&gt;'tom'),
      [3]=array('name'=&gt;'mark')
  )
  </code></pre>
  
  <p>How would i get the last item in the array, and returns it's key.</p>
  
  <p>So in the above example it would return 3.</p>