How to set and read a flash variable?

I'm using this code in the controller and I'm getting an error.

Code:

@session_start();
$_SESSION['notice'] = 'The user has been edited.';
$this->session->mark_as_flash('notice');

Undefined property: Admin::$session
Call to a member function mark_as_flash() on null

Read the documentation.

https://www.codeigniter.com/user_guide/l...sions.html

Sessions will typically run globally with each page load, so the Session class should either be initialized in your controller constructors, or it can be auto-loaded by the system. For the most part the session class will run unattended in the background, so simply initializing the class will cause it to read, create, and update sessions when necessary.

To initialize the Session class manually in your controller constructor, use the $this->load->library() method:

$this->load->library('session');
Once loaded, the Sessions library object will be available using:

$this->session