mod_fcgid: stderr: PHP Fatal error: Class ‘DOMDocument’

You need to install the DOM extension. You can do so on CentOS using:

For php 5.x

yum install php-xml

For php 7.1

yum install php71w-xml

For php 7.2

yum install php7.2-xml

Restart Apache!

systemctl restart httpd

Enjoy!