Hi,
I don't use CentOS, so not sure why this wouldn't just work out of the box if you definitely followed those instructions on the guide.
Did you definitely restart your web server? 'sudo /bin/systemctl reload httpd', and did you definitely install PHP? 'sudo yum install php php-pear'? There should be no harm typing it again and restarting your web server if it did need installing.
The other thing to check is if this line is somewhere in your apache config:
Code:
AddType application/x-httpd-php .php
And see if there is something similar to this too:
Code:
LoadModule php5_module /path/to/your/libphp5.so
I hope this gives you a pointer, and enough to help fix it.
Good luck!