php-pecl-memcache package is not included in the default CentOS repositories. It can be installed from the Remi repository.
In order to install php-pecl-memcache, you need to have root permission.
STEP 1. Enabling the Remi repository
sudo yum install epel-release yum-utils sudo yum install http://rpms.remirepo.net/enterprise/remi-release-7.rpm sudo yum-config-manager --enable remi
STEP 2. Install the mcrypt package by typing:
sudo yum -y install php-pecl-memcache