CentOS installation comes with PHP 5.4 which should upgrade to run websites.

To install a newer version of PHP, follow the easy instruction listed below:

yum install http://rpms.remirepo.net/enterprise/remi-release-7.rpm
yum install yum-utils

For PHP 5.6

yum-config-manager --enable remi-php56

For PHP 7.3

yum-config-manager --enable remi-php73

Now upgrade php

yum -y upgrade php*

Check the php version

php -v

Done !