PHP implementation of the main domain name and two-level domain name sharing session and single sign-on

The company's website set up a number of two domain names, the boss asked no matter which domain name the member went to, the main domain name or level two domain name, users are logged in state, and do not need to log in again.
Obviously, the requirement is a single sign-on.

There are two ways to do this in PHP, which is to save session_id with cookies, each domain name can access the cookie, and then get the session_id:

1. Use the Session_set_cookie_params () method:

Session_set_cookie_params (0, $path, ' abc.com ');

2. Modify the Session.cookie_domain value by using Ini_set or modifying the php.ini:

Ini_set (' Session.cookie_domain ', ' abc.com ')