title: how to add onclick event handler inside highcharts tooltip
body: <p>I am using highcharts ( Line ) in my php application. I want to use onclick event handler inside the tooltip to open the modal dialog. But i don't find any solution for that, even in highcharts there is no click event available for tooltip item. I also used formatter option inside tooltip but it doesn't worked. Please help me in this issue</p>
  
  <p>I am trying this </p>
  
  <pre><code>tooltip: {
      useHtml: true,
      formatter: function () {
          var s = '&lt;b&gt;' + this.x + '&lt;/b&gt;';
          $.each(this.points, function (i, point) {
              s += '&lt;br/&gt;&lt;span style="color:' + point.series.color + '"&gt;\u25CF&lt;/span&gt;\n\ &lt;span onclick="my_function();"&gt;Click Me&lt;/span&gt; ' + point.series.name + ': ' + point.y;
          });
          return s;
      },
      shared: true
  }
  </code></pre>
  
  <p>but my_function is not calling when i click on "Click Me"</p>