Laravel Null dump value

I need to find the data coresponding to a specific id, i keep getting this error, i tried dump the id value and it shows NULL, no idea why, here is code :

Controller :

 function fetchdata(Request $request)
        {
            $id = $request->get('ID');
            $req = Demo::find($id);
            $output = array(
                'reponse'    =>  $req->reponse,
            );
            echo json_encode($output);
        }

View :

$(document).on('click', '.req_reponse', function(){
        var id = $(this).attr("ID");
        $('#form_output').html('');
        $.ajax({
            url:"",
            method:'get',
            data:{id:id},
            dataType:'json',
            success:function(data)
            {
                $('#reponse').val(data.reponse);
                $('#ID').val(id);
                $('#studentModal').modal('show');
            }
        })
    });

Error :

'reponse'    =>  $req->reponse,

    "Trying to get property of non-object"

via Chebli Mohamed