Am I a machochistic fuck?
This sunday I had the glorious idea to fix a not-so-recent Wordpress website for a friend.
Imagine an upgrade from 3.3.2 to 4.9.8! (and PHP 5.5.old to 7.2.new

Oh boy. I thought it was impossible, because the site uses a free theme from 2012 and had some other plugins installed.
But what kind of developer am I, if I give up so easily?

I forced XAMPP to run PHP 5.6.stoneage in order to let me debug this thing. After some fixing in different files, I was able to get the admin panel back, disabled some plugins and then overwrote the installation with WP 4.9.8. After firing up the admin panel I had to fix 20 differend PHP files in the plugins.

Finally! After the plugins were updated, all worked again.
Except for the backend part of this free crappy theme. It uses an old version of JQuery UI widgets with custom mods.
I've done enough for today so I let it be like this. I'm not in the mood to load a second JQuery version.