PHP$_GET在尝试第一个REST请求时为空

为了了解REST，我正在学习/复制一个教程。"$_get"是空白的，我注意到被调用的URL是空白的。这里是一个副本，

http://localhost/RestClient/index.php?action=get_user&id=

但是我点击的href对我来说还可以。

<a href='http://localhost/RestClient/index.php?action=get_user&id='3' alt=user_'3'>Carbonnel</a>

这是我的代码，我是PHP的新手，所以我会边做边计算！！！！

<?php
/*** this is the client ***/
if (isset($_GET["action"]) && isset($_GET["id"]) && $_GET["action"] == "get_user") // if the   get  parameter action is get_user and if the id is set, call the api to get the user information
 {
 $user_info = file_get_contents('http://localhost/RestServer/api.php?action=get_user&id=' .  $_GET    ["id"]);
$user_info = json_decode($user_info, true);
// THAT IS VERY QUICK AND DIRTY !!!!!
?>
<table>
  <tr>
    <td>Name: </td><td> <?php echo $user_info["last_name"] ?></td>
  </tr>
  <tr>
    <td>First Name: </td><td> <?php echo $user_info["first_name"] ?></td>
  </tr>
  <tr>
    <td>Age: </td><td> <?php echo $user_info["age"] ?></td>
  </tr>
 </table>
 <a href="http://localhost/RestClient/index.php?action=get_userlist" >Return to the user list</a>
 <?php
 }
 else // else take the user list
 {
 $user_list = file_get_contents('http://localhost/RestServer/api.php?action=get_user_list');
 $user_list = json_decode($user_list, true);
 // THAT IS VERY QUICK AND DIRTY !!!!!
 ?>
 <ul>
 <?php foreach ($user_list as $user): ?>
  <li>
    <?php echo "<a href='http://localhost/RestClient/index.php?action=get_user&id='".$user ['id']."' alt=user_'".$user['id']."'>"; ?><?php echo $user["name"] . "</a>"; ?>

  </li>
  <?php endforeach; ?>
  </ul>
  <?php
 }
?>