merhaba böyle bir kod yapıya sahip

public static $userId;
public static $checkUserId;
public $chckUserId;
function __CONSTRUCT(){//Constructor 
    parent::__CONSTRUCT();
    self::$userId = $_SESSION["userid"];//Asssign Current Logged In User's UserId
}

this works holding user session then i want to hold one changing session coz i ant to use it in all function of the class i want to be assigned in a public variable , i assigned and worked but not changing what could be the problem? can u please suggest hw can i implement that?