session存储在redis/memcache/mysql
方式1、修改php.ini
;session.save_handler = files
#session.save_handler = redis
#session.save_path = "tcp://127.0.0.1:6379?auth=密码"
session.save_handler = memcached
session.save_path = "localhost:11211"
方式2、ini_set('session.save_handler', 'xxx');