I needed to upgrade PHP from version 5.6.38 to version 7.3 by the recommendation from WordPress, so tried to find the way can do that on my CentOS 7.5 server.

Below is the current version I checked on my CentOS 7.5 server:

$ php -ver
PHP 5.6.38 (cli) (built: Oct 24 2018 12:50:38)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies

Followings are the steps I found

STEP 1.Turn on EPEL repo, enter:

sudo yum -y install epel-release

STEP 2. Turn on Remi repo i.e.remi-php73:

sudo yum-config-manager --enable remi-php73

STEP 3. Refresh repository:

sudo yum update

STEP 4. Install php version 7.2, run:

sudo yum install php