Further research here showed me a thread regarding this issue and provided a “rollback” respository for php 7.1.
FYI to developers – people at “my knowledge level” rely on Nextcloud, but don’t have the time or skill level to catch this sort of thing before it happens. In any event, the rollback solved the problem – but now I have to lock php 7.1 so it doesn’t get auto updated again to 7.2. I don’t know if there is an orderly way to disseminate such information – I had some trouble finding the thread that provided the solution. FYI to other users: apparently Nextcloud 12 is not php 7.2 compatible and with developer focus on Nextcloud 13, won’t be fixed. My original post/help request is as follows:
I’ve been running Nextcloud for several versions and Owncloud before that. My install updated to php 7.2 and all of my repositories have php 7.2, so I don’t have an easy rollback source for 7.1. I found a note here that someone installed Nextcloud 13 because of php 7.2 – is Nextcloud 13 released? It’s not in the opensuse repositories I use, which have Nextcloud 12. Any suggestions? It will be very complicated to rollback to php 5, because I (re)wrote some of my applications to run specifically on php 7, which run on the same server.