Sometimes the callbacks needs access to program data or other information. To avoid messing with global variables, you can pass the additional data to the callback when you connect it. connect('clicked', 'on_ok_clicked', $window, 'some data'); ?>]]> %connect()% returns an number that uniquely identifies the connection made. This can be useful if you want to disable or remove the callback during the execution. connect('clicked', 'on_ok_clicked'); $ok_button->signal_handler_block($conn_id); // disable callback $ok_button->signal_handler_unblock($conn_id); // re-enable callback $ok_button->disconnect($conn_id); // remove callback permanently ?>]]>