Comment 3 for bug 1324828

As a workaround for trusty, you can use unix:///run/php-fpm/php-fpm.sock|fcgi://127.0.0.1:9000/srv/http/ (notice the triple slash on the unix socket). Only problem then is the length of the variable

https://bz.apache.org/bugzilla/show_bug.cgi?id=53218