Custom html with ajax script inside joomla

Question

I'm fairly new to Joomla. I've been working on a site that retrieve data from MySQL and display it using google chart API. The page works fine on a stand alone, however it fails to operate inside Joomla. So far, from the research and the trials I've made, I'm convinced it has something to do with the HTTP Ajax Post method. Currently I'm using Jumi extension to inject my html page to joomla and the part of the script that retrive the data looks like this.

function generateChartData(){

    var jsonData = $.ajax({
      url: "getdata.php",
      dataType: "json",
      async: false
      }).responseText;

      var data = new google.visualization.DataTable(jsonData);        
      }

Any Help is highly appriciated.