pear的auth类，导入不进来，是怎么回事啊，过来人提点下

<?php
require_once ('Command/Auth.php');                                                
function show_login_form()
{                                          
    echo '<b>用PEAR轻松实现身份验证</b><hr />';
    echo '<form method="post">';
    echo '<p>用户名：<input type="text" name="username" /></p>';
    echo '<p>密　码：<input type="password" name="password" /></p>';
    echo '<input type="submit" value="登录" />';
    echo '</form><br />';
}

$options = array('dsn' => 'mysql://root:@localhost/demo');               
$auth = new Auth('DB', $options, 'show_login_form');                  
$auth->start();                                                            
if ($auth->checkAuth())
{                                               
    echo '<b>用PEAR轻松实现身份验证</b><hr />';
    echo '<p>你已经成功登录，并可以访问本页面了！</p>';
} else {                                                            
    echo '<p>你需要登录后才能访问本页。</p>';
}
?>
这段代码出错了Fatal error: Class 'Auth' not found in D:\wamp\www\19\19-2.php on line 16
貌似没有auth这个类，没导入进来额auth.php这个文件，我是把pear下的Command文件夹它复制在同级目录的啊，什么状况。。。。今天才装得pear