如何停止更新订户以更改用户角色

Question

我是php和sql的新手 我有两个用户角色，一个是admin，另一个是订阅者，我想阻止订阅者更新订阅admin的用户角色。其他是如何允许他们更改密码，如果我从配置文件更改密码，则无法使用更改后的密码再次登录 代码是从“ https://github.com/mindaras/PHP-custom-CMS-for-simple-blog”下载的

          <?php
            if (isset($_SESSION['username'])) {
              $user_id = $_SESSION['user_id'];

              $query = "SELECT * FROM users WHERE user_id = '{$user_id}'";
              $result = mysqli_query($connection, $query);

              if (!$result) {
                die(mysqli_error($connection));
              }

              $row = mysqli_fetch_assoc($result);

              $username = $row['username'];
              $user_firstname = $row['user_firstname'];
              $user_lastname = $row['user_lastname'];
              $user_role = $row['user_role'];
              $user_password = $row['user_password'];
              $user_email = $row['user_email'];
              $user_image = $row['user_image'];
            }
          ?>
          <?php
            if (isset($_POST['update_profile'])) {
              $user_id = $_SESSION['user_id'];
              $username = $_POST['username'];
              $user_firstname = $_POST['user_firstname'];
              $user_lastname = $_POST['user_lastname'];
              $user_role = $_POST['user_role'];
              $user_password = $_POST['user_password'];
              $user_email = $_POST['user_email'];
              $user_image = $_FILES['image']['name'];
              $user_image_temp = $_FILES['image']['tmp_name'];

              move_uploaded_file($user_image_temp, "../images/{$user_image}");

              $query = "UPDATE `users` SET ";
              $query .="username = '{$username}', ";
              $query .="user_firstname = '{$user_firstname}', ";
              $query .="user_lastname = '{$user_lastname}', ";
              $query .="user_role = '{$user_role}', ";
              $query .="user_password = '{$user_password}', ";
              $query .="user_email = '{$user_email}', ";
              $query .="user_image = '{$user_image}' ";
              $query .="WHERE user_id = {$user_id}";

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

              if (!$result) {
                die(mysqli_error($connection));
              }
            }
          ?>