HUBzero still requires the use of PHP 5.6 (7.x support coming soon).  For CentOS/RedHat 7 you used to be able to get 5.6 via the software collections library and when that was removed we mirrored a copy. These packages are no longer being maintained so are not recommended. The current recommendation for RedHat/CentOS 7 is to use the php56 packages from the Remi Repository (https://rpms.remireponet). These packages are still receiving security updates for serious issues despite PHP 5.6 reaching upstream EOL.

sudo rpm -Uvh https://rpms.remirepo.net/enterprise/remi-release-7.rpm
sudo yum install -y hubzero-php56-remi
sudo service php56-php-fpm start
sudo chkconfig php56-php-fpm on