public static function addUser($db, $login, $password, $firstName, $familyName)
 {
     $instance = new self($db);
     $hash = $instance->generateRegisterHash($login);
     $password = password_hash($password, PASSWORD_DEFAULT);
     if ($instance->isLoginAvailable($login)) {
         $result = $instance->myDB->query($instance->SQL_CREATE_USER, array('login' => $login, 'password' => $password, 'familyName' => $familyName, 'firstName' => $firstName, 'hash' => $hash));
         if ($result != 0) {
             $instance->userId = $instance->myDB->lastInsertId();
             $instance->username = $login;
             require "../misc/registrationMail.php";
             require "../misc/mailFunc.php";
             sendRegistrationMail($login, $hash);
             return $instance;
         }
     }
     return null;
 }