6
First I looked for the template which is responsible for the notification block (system_notification_select.html).
Whithin the template there is the variable $xoops_notification.show
I did a search of $xoops_notification over the XOOPS sources and found some entries. The right file was notificaton_select.php, because here we have the following line:
if ($xoops_notification['show']) {
This was the entry point for debugging. (BTW, I use the ActiveState Komodo IDE for debugging, which is not too expensive for personal use. Don't know if there is something equivalent for free.)
In advance of the debugging I found that the function notificationSubscribableCategoryInfo() did not give back any notification categories.
Then I debugged into notificationSubscribableCategoryInfo () and was wondering about the variable $script_name having php.exe.
I included a phpinfo () command into my internet and into my local site and compared the _SERVER variables, and voila, the local site showed something different.
I found that the _SERVER['SELF_PHP'] on my local site did show the correct path.
But please dont't ask me about the correct values and meanings of the php _SERVER[] vars.