+function tab_changed($name)
+{
+ $to = find_submit("{$name}_", false);
+ if (!$to) return null;
+
+ return array('from' => $from = get_post("_{$name}_sel"),
+ 'to' => $to);
+}
+/*
+ Check whether tab has been just switched on
+*/
+function tab_opened($name, $tab)
+{
+ return (get_post('_'.$name.'_sel') != $tab) && (find_submit($name.'_', false) == $tab);
+}
+/*
+ Check whether tab has been just switched off
+*/
+function tab_closed($name, $tab)
+{
+ return (get_post('_'.$name.'_sel') == $tab) && (find_submit($name.'_', false) != $tab);
+}
+/*
+ Check whether tab is visible on current page
+*/
+function tab_visible($name, $tab)
+{
+ $new = find_submit($name.'_', false);
+ return (get_post('_'.$name.'_sel') == $tab && !$new) || $new==$tab;
+}
+