Comment 2 for bug 1674892

If you wouldn't mind testing: https://launchpad.net/~nacc/+archive/ubuntu/php7testbuilds has 7.0.17 for xenial. Please do no run this in production, but see if it resolves your issue.

If it does, and given the small fix needed, I can probably squeeze this in during the freeze if it's urgent on your end (it will still take at least a week to make it in to 16.04).