[BleverCastard]

I'm learning mysqli and when creating a URL Shortener I get this error: Call to a member function real_escape_string() on a non-object on this line:

PHP код:

$url = $this->db->escape_string($url); 


PHP код:

class Shortener {
    protected $db;
    public function _construct()  {
        $this->$db = new mysqli('localhost', 'root', '*****', 'shortn');
    } 


I have not forgot to close the class before any one tries to point that out.