Undefined index in Sessions please help?

Question

PHP

Tell me, please, what is the problem?

Notice: Undefined index: telephone in
Notice: Undefined index: idUser in

$sql = "SELECT * FROM `users` WHERE mail = '$mail'";
    $row =  mysqli_query($db, $sql);
    $res = mysqli_fetch_assoc($row);
    if($mail == $res['mail'] && $password == $res['password']){
        $_SESSION['id'] = $res['id'];
        $_SESSION['fname'] = $res['fname'];
        $_SESSION['lname'] = $res['lname'];
        $_SESSION['telephone'] = $res['telephone'];
        $_SESSION['idUser'] = $res['idUser'];
        $_SESSION['mail'] = $res['mail'];
        $_SESSION['password'] = $res['password'];
        $_SESSION['start'] = time();
        $_SESSION['expire'] = $_SESSION['start'] + (60 * 60);
        header("Location: ../personalPage.php");
    }

<?php 
 
session_start();
if (!isset($_SESSION['id'])) {
  header("Location: index.php");
}
else{
  $now = time();
  if ($now > $_SESSION['expire']) {
    session_destroy();
    header("Location: index.php");
    echo "
            <script>
                alert('Ձեր ժամանակն սպառվեց!');
                window.location.href = 'index.php';
            </script>
        ";
  }
  else{ ?>

<ul>
  <li><a href="#?"><?= $_SESSION['fname'] . " " . $_SESSION['lname'];?></a></li>
  <li>Հասցե - <a href="#">Qaghaq Armavir</a></li>
  <li>Հեռ․ - <a href="#">		<?= $_SESSION['telephone'];?></a></li>
  <li>Էլ․ հասցե - <a href="#"><?= $_SESSION['mail'];?></a></li>
  <li>ID - <a href="#n">		<?= $_SESSION['idUser'];?></a></li>
</ul>

<?php
  }
}
?>