(PHP 5 >= 5.4.0)
SessionHandlerInterface::write — Write session data
Writes the session data to the session storage. Called by session_write_close(), when session_register_shutdown() fails, or during a normal shutdown. Note: SessionHandlerInterface::close() is called immediately after this function.
PHP will call this method when the session is ready to be saved and closed. It encodes the session data from the $_SESSION superglobal to a serialized string and passes this along with the session ID to this method for storage. The serialization method used is specified in the session.serialize_handler setting.
Note this method is normally called by PHP after the output buffers have been closed unless explicitly called by session_write_close()
The session id.
The encoded session data. This data is the result of the PHP internally encoding the $_SESSION superglobal to a serialized string and passing it as this parameter. Please note sessions use an alternative serialization method.
会话存储的返回值（通常成功返回 0，失败返回 1）。