php cache collisions for chroot mode php-fpm

Need to set validate_root option on for php-fpm using chroot (or always? does it hurt performance or anything?)

See https://www.howtoforge.com/community/threads/apache-serving-wrong-vhost.85620/page-2#post-416357 and https://www.howtoforge.com/community/threads/serving-wrong-website-sporadically.86962/#post-422491