使用查询中的表单执行查询更新

我正试图在我的用户列表页面上创建一个按钮来删除该行，或者让该用户成为管理员。

以下是用户查询和html:的信息

    <?php
      $query = "SELECT * FROM users";
      try
      {
      $stmt = $db->prepare($query);
      $result = $stmt->execute();
      }
      catch(PDOException $ex)
      {
      die("An Error has occured. Please contact the server administrator for assistance.");
      }             
      $rows = $stmt->fetchAll();
    ?>
    <?php foreach($rows as $row) : ?>
    <?php
    if($row['usertype'] == 2) {
      $usertype = "<span style='color:#F7FE2E;'>Donator</span>";
    } elseif($row['usertype'] == 3) {
      $usertype = "<span style='color:red;'>Admin</span>";
    } elseif($row['usertype'] == 4) {
      $usertype = "<span style='color:orange;'>Owner</span>";
    } else {
      $usertype = "<span style='color:#585858;'>Normal</span>";
    }
    ?>
    <tr>
    <!--<td><?php echo $row['id']; ?></td>-->
    <td><?php echo htmlentities($row['username'], ENT_QUOTES, 'UTF-8');?></td>
    <!--<td><?php echo htmlentities($row['email'], ENT_QUOTES, 'UTF-8');?></td>-->
    <td><?php echo htmlentities($row['steamid'], ENT_QUOTES, 'UTF-8');?></td>
    <td><?php echo $usertype?></td>
    <td><form action="" method="post">
    <input type="submit" name="admin" value="Promote" />
    </form></td>
    </tr>
    <?php endforeach; ?>

以及我准备和执行更新查询的代码：

        if(!empty($_POST['admin']))
        {
            $query = "UPDATE `users` SET `usertype` = '3' WHERE `id` = " . $row['id'];
            // $query_params = array(':id' => $row['id']);
          try
          {
            $stmt = $db->prepare($query);
            $result = $stmt->execute();
          }
          catch(PDOException $ex)
          {
            die("An Error has occured. Please contact the server administrator for assistance.");
          }
        }

不幸的是，当我运行当前设置时，它会更新最后一行。为了进一步询问我在寻找什么，我是否有一个用户列表：其中"admin_b"是强制$_POST['admin'] 的按钮

1. 比利admin_b
2. Bob admin_b
3. Jill admin_b
4. 千斤顶admin_b

更新：

因此，在我的表单中，我有一个<input type="hidden" name="id" value="<?php $row['id']; ?>" />的输入，并将其添加到我的SQL $query = "UPDATE users SET usertype = '3' WHERE id = :id"; $query_params = array(':id' => $_POST['id']); 中

try { $stmt = $db->prepare($query); $result = $stmt->execute(); } catch(PDOException $ex) { die("An Error has occured. Please contact the server administrator for assistance."); }