I had to install 'devel/php56-json' manually for Baikal to work.
A commit references this bug: Author: mat Date: Fri Sep 30 13:20:06 UTC 2016 New revision: 422982 URL: https://svnweb.freebsd.org/changeset/ports/422982 Log: Add php-json to the dependencies. PR: 213097 Reported by: optikfluffel Sponsored by: Absolight Changes: head/www/baikal/Makefile