Error with email class in CI 3.1.8

i can't understand what's your mean by $this->email = "examplestring" and attribute $email = "examplestring"
can you please give me a sample code?

even im doing the same on another project with CI 3.1.5 and it works. idk why is not working in 3.1.8 !

The E-Mail Class work on 3.1.8. I have tested it.

PHP Code:

class Example extends CI_Controller {

    function __construct() {
        parent::__construct();
        
        $this->email = 'example'; // this is the problem. remove this line
    }

    public function send_example_email()
    {

        $this->email = 'example'; // this is the problem. remove this line
        
        /* You E-Mail Code*/
    }
} 


print the value $this->email