title: Highcharts Tooltip - Access "z" value in series data array
body: <p>I'm working with Highcharts and I'm trying to display the <code>this.z</code> value (if possible) in the <code>tooltip:formatter</code> section.</p>
  
  <p>This is an example of the json array from  PHP I am passing back to a callbackfunction in javascript:</p>
  
  <pre><code>[1315713600000,20,100]
  </code></pre>
  
  <p>I am able to access <code>this.x</code> (1315713600000) and <code>this.y</code> (20) in the tooltips, but cannot access <code>this.z</code> (100) if it's at all possible.</p>
  
  <p>Any ideas?</p>