How to create a simple vote by ajax in CakePHP 2.0

Question

I am just trying to create a simple vote with CakePHP 2.0 and Ajax. I am a newbie in this framework so i find it really difficult...

I just want to create a link with a vote action which will call an action in a controller to update the field "numberVotes" in a table of the Database.

I am trying it but i dont know if i am doing it well. I have this now:

//posts/view.ctp $this->Html->script('votar', array('inline' => false)); //it loads it on the layout

echo '<div id=\'vote\'>';
    echo $this->element('vote', array('id' => $post['Post']['id']));
echo '</div>'

Elements/vote.ctp

if(!empty($voting)){
echo "You have voted!!!";   
}else{
echo '<a href="#" onclick="votar(\''.$id.'\');return false;">Vote here!!</a>
}

webroot/js/vote.js

//XMLHttpRequest  Ajax
function newAjax()
{ 
var xmlhttp=false; 
try 
{ 
    xmlhttp=new ActiveXObject("Msxml2.XMLHTTP"); 
}
catch(e)
{ 
    try
    { 
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); 
    } 
    catch(E) { xmlhttp=false; }
}
if (!xmlhttp && typeof XMLHttpRequest!='undefined') { xmlhttp=new XMLHttpRequest();     } 
return xmlhttp; 
}


function voting(num) {
var url;
var obCon = document.getElementById('vote');
var ajax = newAjax();

url = 'http://localhost:8888/mysite/posts/voting/' + num;
alert(url);
ajax.open("GET", url);  

ajax.onreadystatechange=function(){
    if(ajax.readyState==4){
        if(ajax.status==200){
            obCon.innerHTML=ajax.responseText;

        }else if(ajax.status==404){
            obCon.innerHTML = "Page not found";
        }else{
            obCon.innerHTML = "Error:"+ajax.status; 
        }
    }
}
ajax.send(null);

}

//Controllers/PostsController.php

public function voting($id = null){
            ... //stuff to add the vote in the DB
    $this->set(array('id' => $id, 'voting' => 'yes'));
    $this->render('/Elements/vote', false);
}

I am sure i am not using the power of CakePHP for ajax... but i dont know where i can apply it or how to do it. Any suggestion?

Thanks.