I'm finding the Most Users Ever Online count keeps resetting to zero and to today's date
It could be related to your server or some specific issue, nobody will tell you precisely what is the reason. As you see on our board or somewhere else, "Most Users Ever Online" keeps in place all the time with no problem. It could be related to something which removes the add-on's file, but without deep debugging I have no ideas.
The code you have mentioned may be useful for admin only. It is not documented anywhere, because it's kind of a hidden feature which allows to reset "Most Users Ever Online" directly from the browser. But it will work only if you as an Admin are logged in
, i.e. your $user_id is 1. Then you could manually type /addon_whosonline.php?resetwonline=1
and the data will be reset.
I didn't understand the issues about search, if I type "who's online
" it merely works.