Refactor away from using wonderfall parent image
This image's base, wonderfall/nginx-php, hasn't been updated for 3 months, and this should probably be rebased on one that will receive updates.
Haven't done much digging yet, but it might even be possible to rebase this on top of the docker library php-fpm image, which would be most frequently updated with new versions and patches.
This would, of course, need to be accompanied by extensive feature and stability testing to ensure the switch is safe. The last thing I'd want to happen is to break people's existing installs with a minor update.
Maybe this should get more attention, now that a security threat has been discovered? (see https://nextcloud.com/blog/urgent-security-issue-in-nginx-php-fpm/)
Alternatively, you could switch to hoellen's php-image, which seems up-to-date? (see https://github.com/hoellen/dockerfiles)