yum install memcached

service memcached start or maybe: systemctl start memcached.service

pecl install memcache

systemctl restart httpd.service

If you want install from source:

wget http://pecl.php.net/get/memcache
cd memcache*
phpize
./configure
make && make install

echo “extension=memcache.so” >> /your_path/php.ini