This one is quite simple to be honest. Assuming you have Redis already installed and set up correctly you can just change your php-fpm pool definition to include:
php_value[session.save_handler] = redis php_value[session.save_path] = "tcp://127.0.0.1:6379"
If you’re using password for logging into redis you would specify it like:
php_value[session.save_path] = "tcp://127.0.0.1:6379?auth=PASSWORD"
Restart php-fpm after that:
service php-fpm restart
and you should now see PHP saving sessions within Redis service:
127.0.0.1:6379> keys PHPREDIS_SESSION* 1) "PHPREDIS_SESSION:GFtHQ69XH6C7xe5LLYzhJ35zUQACJw" ...