To install PHP 5.6, you have to install and enable EPEL and Remi repository.
# yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
# yum install http://rpms.remirepo.net/enterprise/remi-release-7.rpm
# yum install yum-utils
If you want to install PHP 5.5, PHP 5.6 or PHP 7.2 on CentOS 7, just enable it and install as shown.
# yum-config-manager –enable remi-php55 [Install PHP 5.5]
# yum-config-manager –enable remi-php56 [Install PHP 5.6]
# yum-config-manager –enable remi-php72 [Install PHP 7.2]
We have chosen to install PHP 5.6.
# yum-config-manager –enable remi-php56 [Install PHP 5.6]
# yum install php php-mcrypt php-cli php-gd php-curl php-mysql php-ldap php-zip php-fileinfo
Afterwards, double check the installed version of PHP on your system.
# php -v