Previously i posted about upgrading PHP 5.3 to PHP 5.6 on CentOS 6.
If you want to install / upgrade it to PHP 7, here’s how:

1. Make sure to remove older version of PHP
yum remove php-common

2. Add EPEL and Remi repository
yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-6.noarch.rpm
yum install http://rpms.remirepo.net/enterprise/remi-release-6.rpm

3. Install yum-utils
yum install yum-utils

4. Enable Remi repository
yum-config-manager --enable remi-php72

5. Now install PHP 7
yum install php php-xml php-mcrypt php-cli php-gd php-curl php-mysql php-ldap php-zip php-fileinfo

6. When it’s done, restart your web server (apache or nginx)

7. Check your PHP version
php -v

Hope it helps.