I also have issues with libxml2 even though I believe my system is up-to-date, including mirror list.
$ sudo pacman-mirrors --fasttrack && sudo pacman -Syu
...
$ php -v
php: error while loading shared libraries: libxml2.so.2: cannot open shared object file: No such file or directory
$ yay -S libxml2-legacy
-> No AUR package found for libxml2-legacy
there is nothing to do
Also did a system restart between refreshing mirrors and the other commands.