Laravel update MySql table failure

I need to update MySql table from Laravel view but when i submit the update the success message is displayed but nothing is updated inside MySql table or the view, the console log does not show any error. Here is code :

Controller :

public function reponse(Request $request)
    {
        $validation = Validator::make($request->all(), [
            'reponse' => 'required',
        ]);

        $error_array = array();
        $success_output = '';
        if ($validation->fails())
        {
            foreach ($validation->messages()->getMessages() as $field_name => $messages)
            {
                $error_array[] = $messages; 
            }
        }
        else
        {
            $student = Demo::find($request->get('ID'));
            $student->reponse = $request->get('reponse');
            $student->save();
            $success_output = '<div class="alert alert-success">Data Updated</div>';
        }

        $output = array(
            'error'     =>  $error_array,
            'success'   =>  $success_output
        );
        echo json_encode($output);
    }

View :

$('#student_form').on('submit', function(event){
        event.preventDefault();
        var form_data = $(this).serialize();
        console.log($('#reponse').val());
        $.ajax({
            url:"",
            method:"GET",
            data:form_data,
            dataType:"json",
            success:function(data)
            {
                if(data.error.length > 0)
                {
                    var error_html = '';
                    for(var count = 0; count < data.error.length; count++)
                    {
                        error_html += '<div class="alert alert-danger">'+data.error[count]+'</div>';
                    }
                    $('#form_output').html(error_html);
                }
                else
                {
                    $('#form_output').html(data.success);
                    $('#student_form')[0].reset();
                    $('#req_table').DataTable().ajax.reload();
                }
            }
        })
    });

via Chebli Mohamed