Wordpress get_用户返回用户id而不是名称

我正在使用'get_users'生成一个数组或所有WordPress用户，角色为'moderator'，我的代码如下所示

<?php
    $args  = array(  
    'fields' => 'first_name',
    'role' => 'moderator'  
    );
    $temp = get_users($args);
?>
    <?php foreach ($temp as $i => $item): ?>
    <input type="checkbox" name="<?php $mb->the_name(); ?>" value="<?php echo $item; ?>"<?php $mb->the_checkbox_state($item); ?>/> <?php echo $item; ?><br/>
    <?php endforeach; ?>

<?php
    $args  = array(  
    'fields' => 'first_name',
    'role' => 'moderator'  
    );
    $temp = get_users($args);
    foreach($temp as $user) {
        echo '<li>' . $user->display_name . '</li>';
    }
?>

[ID] => 1
[user_login] => admin
[user_pass] => $P$Bxudi6gJMk2GRt2ed3xvZ06c1BPZXi/
[user_nicename] => admin
[user_email] => admin@host.com
[user_url] => http://localhost/
[user_registered] => 2010-06-29 07:08:55
[user_activation_key] => 
[user_status] => 0
[display_name] => Richard Branson