To install php_intl , first you must install the Remi repository. Remi repository is a free repository providing many cutting edge latest versions of software which are not available in your CentOS installation and or repository by default.
Login to your server as root or as a user with root privilege (sudo) via your favorite SSH.
For CentOS/RHEL/Scientific Linux 7 x86_64
rpm -Uvh remi-release-7.rpm
yum –enablerepo=remi install php-intl
To permanently enable remi repo , run the following command:
and set enabled=1
To check if you have the php-intl extension installed, run the command:
php -m | grep intl
Source: How to install extenion php_intl in centos7 x86_64?