求助：session_regenerate_id(): Failed to create(read) session ID: user？？

z追梦

代码如下：$this->load->library('session');
$user_info = array(
    'id' => 1,
    'age' => 29,
    'sex' => '男'
);
$this->session->set_userdata($user_info);
$result = $this->session->userdata('age');
var_dump($result);

加载session后获取session存储数据正常，但是每五分钟左右会报一次警告：
A PHP Error was encountered

Severity: 4096

Message: session_regenerate_id(): Failed to create(read) session ID: user (path: )

Filename: Session/Session.php

Line Number: 720

int(29)


使用：
php由5.3升级到php7CodeIgniter3.15
请各位朋友帮忙看看该如何解决.

z追梦

有朋友遇到过这种问题吗？请帮帮忙