how to catch data in CI with basic Ajax

[eluser]ludo31[/eluser]
I try to make like that but nothing run !!

Code:

xmlhttp.open("GET", "ajaxcontrolleur?q="+str, true);

and sometimes change the way to catch

Code:

//  $q = $_GET["q"];
        
       $this->input->get('q');

I don't know if we must create another view file or we need to redirect in first view file