title: Return index of highest value in an array
body: <p>From an array that looks something like the following, how can I get the index of the highest value in the array. For the array below, the desired result would be '11'.</p>
  
  <pre><code>Array (
      [11] =&gt; 14
      [10] =&gt; 9
      [12] =&gt; 7
      [13] =&gt; 7
      [14] =&gt; 4
      [15] =&gt; 6
  )
  </code></pre>