Three days had passed and still having problems to get this things work. This AJAX Call on my js file seems working when it comes to sending JSON data:
var
Can you see the ajax request data using the firebug console?
You cannot get the lastname, firstname from $_POST. It's inside the json string. First, you have to get the data using
$data = $_POST['data'] or $_REQUEST['data']
Then, decode the $data using json_deocde and access your attributes.
json_decode($data);