Permission Denied to PHP Files on Centos 7 with nginx
Check to make sure your php config doesn't have any syntax errors or permissions problems - I'm not familiar with Centos7 but in Ubuntu 14.04 it's sudo /usr/sbin/php-fpm7.0 --fpm-config /etc/php/7.0/fpm/php-fpm.conf
that will tell you if there are any errors. When I've ran into this problem in the past, it was because the directory PHP-FPM was trying to write the PID file to didn't exist.