(PHP 5 >= 5.4.0, PHP 7)
SessionHandlerInterface::open — Initialize session
$save_path
, string $session_name
) : boolRe-initialize existing session, or creates a new one. Called when a session starts or when session_start() is invoked.
save_pathThe path where to store/retrieve the session.
session_nameThe session name.
会话存储的返回值（通常成功返回 0，失败返回 1）。