HTTP Request and checkbox table update

Earlier thread (530843 - Feb 2008) showed technique for using a HTTP request to immediately update a MySQL table using checkboxes in a php form. However this technique seems to work only for updating the table when the checkbox is checked and does not seem to update when the checkbox is unchecked. Is there a way to update the table when the checkbox is unchecked? Is there a better way to develop php forms that that immediately update the database table when a form checkbox is checked or unchecked?