(PHP 5 >= 5.4.0)
SessionHandler::open — Initialize session
$save_path
, string $session_id
)Create new session, or re-initialize existing session. Called internally by PHP when a session starts either automatically or when session_start() is invoked.
This method wraps the internal PHP save handler defined in the session.save_handler ini setting that was set before this handler was set by session_set_save_handler().
If this class is extended by inheritiance, calling the parent open method will invoke the
wrapper for this method and therefor invoke the associated internal callback. This allows this method to be
overidden and or intercepted and filtered.
For more information on what this method is expected to do, please refer to the documentation at SessionHandlerInterface::open().
save_path
The path where to store/retrieve the session.
session_id
The session id.
会话存储的返回值（通常成功返回 0，失败返回 1）。