By default the latest PHP version CentOS 7 supports is something along the lines of 5.6.14. However there is already a 7.2 version out at this time. If you just downloaded WordPress, after its installation you'll notice it wants a newer version than the 5.6.14.

For this I used this website: https://blog.remirepo.net/post/2017/12/04/Install-PHP-7.2-on-CentOS-RHEL-or-Fedora and the webpage actually has instructions to install PHP 7.2 on quite a few Linux distributions.

Before starting the whole upgrading thing, make sure you're root:

sudo -i

Getting the necessary repositories and telling the system about them:

wget https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
wget http://rpms.remirepo.net/enterprise/remi-release-7.rpm
rpm -Uvh remi-release-7.rpm epel-release-latest-7.noarch.rpm

Activating PHP 7.2

yum install yum-utils 
yum-config-manager --enable remi-php72

Aand upgrade!

yum update

Done

You can check the version like this :

php -v

For me that didn't work one time, so I just repeated the whole process again and all of a sudden it worked ¯\_(ツ)_/¯