Why doesn't function confirm change 0 to 1 in the database when confirming registration?

Question

PHP

function confirm()
{
    global $db;
    $new_hash = clear_str($_GET['hash']);

    $query = "UPDATE . PREF .`users` SET confirm = '1' WHERE `hash` = '%s'";

    $query = sprintf($query, mysqli_real_escape_string($db, $new_hash));

    $resutl = mysqli_query($db, $query);


    if (mysqli_affected_rows($resutl) == 1) {
        return TRUE;
    } else {
        return "Не верный код подтверждения регистрации";
    }


}

?>

if($_GET['hash']) {

  $confirm = confirm();

  if($confirm === TRUE) {
    $_SESSION['msg'] = "Ваша учетная запись активирована. Можете авторизироваться нга сайте.";
    header("Location:".$_SERVER['PHP_SELF']);
    exit();
  }
}
else {
  $_SESSION['msg'] = $msg;
  header("Location:".$_SERVER['PHP_SELF']);
  exit();
}

Registration is successful, it sends a registration link, but then it is not possible to follow the link to successfully confirm the registration, what is the reason?

Answer 1

mysqli_affected_rows($db)
php.net/manual/ru/mysqli.affected-rows.php

Answer 2

I already found an error, I just deleted the name localhost from the link that comes to the mail.
But now the error

function confirm()
{
    global $db;
    $new_hash = clear_str($_GET['hash']);

    $query = "UPDATE " . PREF . "users
        SET confirm='1'
        WHERE hash = '%s'
        ";
    $query = sprintf($query, mysqli_real_escape_string($db,$new_hash));

    $result = mysqli_query($db,$query);

    if(mysqli_affected_rows() == 1){
        return TRUE;
    }
    else {
        return "Неверный код подтверждения регистрации";
    }


}

mysqli_affected_rows() expects parameter 1 to be mysqli
What parameter is it asking for?