public function updateNotificationUsername() {
        if (!isset($_POST['newusername'], $_POST['password'])) {
            return '<div class="alert-warning"><span class="closebtn" onclick="this.parentElement.style.display=\'none\';">&times;</span>Invalid Input.</div><br/>';
        }

        if (strlen($_POST['newusername']) <= 4) {
            return '<div class="alert-warning"><span class="closebtn" onclick="this.parentElement.style.display=\'none\';">&times;</span>Your new username must be longer!</div><br/>';
        }

        if (strlen($_POST['newusername']) >= 20) {
            return '<div class="alert-warning"><span class="closebtn" onclick="this.parentElement.style.display=\'none\';">&times;</span>Your new username must be shorter!</div><br/>';
        }

        $password = $this->_database->prepare('SELECT id FROM users WHERE Password = ?');
        $password->execute([
            hash_salt($escaped = escape($_POST['password']), $this->getData('Username'))
        ]);

        if ($password->rowCount() === 0) {
            return '<div class="alert-warning"><span class="closebtn" onclick="this.parentElement.style.display=\'none\';">&times;</span>The user does either not exist or is not logged in.</div><br/>';
        }

        if ($this->getData('Coins') <= 1999) {
            return '<div class="alert-warning"><span class="closebtn" onclick="this.parentElement.style.display=\'none\';">&times;</span>You don\'t have enough coins.</div><br/>';
        }

        $update = $this->_database->prepare('UPDATE users SET Username = ?, Password = ?, Coins = Coins - 2000 WHERE id = ?');
        $update->execute([$user = escape($_POST['newusername']), hash_salt($escaped, $user), $_SESSION['user_id'] ]);

        return '<div class="alert-success"><span class="closebtn" onclick="this.parentElement.style.display=\'none\';">&times;</span>You have successfully changed your username!</div><br/>';
    }