Gallery 3
From Elch-Wiki
Even though Gallery 3 is in hibernation, I am still using it.
After upgrading my system to PHP 7, it just stopped working. After some debugging, I found that I had it configured to use MySQL via the classic "mysql" driver. However, this is no longer part of PHP. So I had to change the file "var/Database.php" to use 'type' => 'mysqli' instead. Now it works again. :)