Ajax not working in opencart 2.0.2.0

Question

I'm having trouble migrating an add on that i built for opencart 1.5.6.1 to opencart 2.0.2.0. the only thing i see differing from the two versions is the imports in the header. i have a function loading something using ajax. in 1.5.6.1 it's working perfectly. in 2.0.2.0 it says

Failed to load resource: the server responded with a status of 500 (Internal Server 

open cart header 1.5.6.1

<script type="text/javascript" src="catalog/view/javascript/jquery/jquery-1.7.1.min.js"></script>
<script type="text/javascript" src="catalog/view/javascript/jquery/ui/jquery-ui-1.8.16.custom.min.js"></script>
<link rel="stylesheet" type="text/css" href="catalog/view/javascript/jquery/ui/themes/ui-lightness/jquery-ui-1.8.16.custom.css" />
<script type="text/javascript" src="catalog/view/javascript/common.js"></script>

open cart header 2.0

<script src="catalog/view/javascript/jquery/jquery-2.1.1.min.js" type="text/javascript"></script>
<script src="catalog/view/javascript/jquery/ui/jquery-ui-1.8.16.custom.min.js"></script>
<link href="catalog/view/javascript/bootstrap/css/bootstrap.min.css" rel="stylesheet" media="screen" />
<script src="catalog/view/javascript/bootstrap/js/bootstrap.min.js" type="text/javascript"></script>
<link href="catalog/view/javascript/font-awesome/css/font-awesome.min.css" rel="stylesheet" type="text/css" />
<link href="//fonts.googleapis.com/css?family=Open+Sans:400,400i,300,700" rel="stylesheet" type="text/css" />
<link href="catalog/view/theme/default/stylesheet/stylesheet.css" rel="stylesheet">

the ajax part of my function

if (window.XMLHttpRequest) {
        // code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp=new XMLHttpRequest();
      } else { // code for IE6, IE5
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
      xmlhttp.onreadystatechange=function() {
        if (xmlhttp.readyState==4 && xmlhttp.status==200) {
           // do my stuff here
        }            
      }
      xmlhttp.open("GET","index.php?route=account/projects/getEncryptedLink"+metafix,true);
      xmlhttp.send();  
}