如何根据用户的电子邮件获取主键?PHP和MYSQL

这是用户登录时的代码:

if (isset($_POST['login_user'])) {
  $email = mysqli_real_escape_string($db, $_POST['Email']);
  $password = mysqli_real_escape_string($db, $_POST['Password']);

  if (empty($email)) {
    array_push($errors, "email is required");
  }
  if (empty($password)) {
    array_push($errors, "Password is required");
  }

  if (count($errors) == 0) {
    $password = md5($password);
    $query = "SELECT * FROM organisers WHERE email='$email' AND password='$password'";
    $results = mysqli_query($db, $query);

    if (mysqli_num_rows($results) == 1) {
      $_SESSION['email'] = $email;
      $_SESSION['success'] = "You are now logged in";
      header('location: loggedInInterface/loggedIN.php');
    }else {
        array_push($errors, "Wrong email/password combination");
    }
  }
}

别担心,我稍后会清理我的代码。 如您所见,他们将使用电子邮件和密码登录。如何获取用户主键值?

注意:主键列名='OrganizerId'