首先要在functions.php注册小工具
添加如下代码：

//侧栏登录小工具
add_action('widgets_init', 'jv_loginwidget_init');
function jv_loginwidget_init() {
    register_widget('jv_loginwidget');
}
class jv_loginwidget extends WP_Widget {
    function jv_loginwidget() {
        $widget_ops = array('description' => '用户登录小工具');
        $this->WP_Widget('jv_loginwidget', 'INLO-用户登录', $widget_ops);
    }
    function widget($args, $instance) {
        extract($args);
?>
<section class="widget">
<?php
    global $user_ID, $user_identity, $user_email, $user_login;
    get_currentuserinfo();
    if (!$user_ID) {
?>
<h3 class="widget-title">用户登录</h3>
<div class="jv-custom">
<form class="jv-login-custom" action="<?php echo get_option('siteurl'); ?>/wp-login.php" method="post">
<p><label><span class="inlojvicon inlojvicon-user"></span> 用户名：<input class="text" type="text" name="log" id="log" value="" size="14" placeholder="输入用户名..."/></label></p>
<p><label><span class="inlojvicon inlojvicon-log-in"></span> 密　码：<input class="text" type="password" name="pwd" id="pwd" value="" size="14" placeholder="输入密码..."/></label></p>
<p><input class="login_btn" type="submit" name="submit" value="登　录" />　<a class="l-url" href="<?php echo get_option('siteurl'); ?>/wp-login.php?action=register" target="_blank" rel="nofollow">注 册</a> | <a href="<?php echo get_option('siteurl'); ?>/wp-login.php?action=lostpassword" target="_blank" class="l-url" rel="nofollow">忘记密码？</a></p>
</form>
</div>
<?php } else { ?>
<h3 class="widget-title">后台管理</h3>
<div class="jv-custom jv-login-custom">
<div class="jv_avatar">
<?php echo get_avatar( get_the_author_meta('ID'), '65' ); ?>
</div>
<div class="jv_li">
    <li><a class="l-url" href="<?php bloginfo('url') ?>/wp-admin/post-new.php" rel="nofollow" target="_blank"><span class="inlojvicon inlojvicon-edit"></span> 撰写文章</a></li>
    <li><a class="l-url" href="<?php bloginfo('url') ?>/wp-admin/edit-comments.php" rel="nofollow" target="_blank"><span class="inlojvicon inlojvicon-comment"></span> 管理评论</a></li>
    <li><a class="l-url" href="<?php bloginfo('url') ?>/wp-admin/" rel="nofollow" target="_blank"><span class="inlojvicon inlojvicon-cog"></span> 控制面板</a></li>
    <li><a class="l-url" href="<?php echo wp_logout_url( $current_url ); ?>" rel="nofollow" target="_blank"><span class="inlojvicon inlojvicon-log-out"></span> 注销登录</a></li>
</div>
</div>
<?php } ?>
</section>
<?php    
    }
    function form($instance) {
        global $wpdb;
?>
    <p>此工具无需设置</p>
<?php
    }
}

然后就可以在小工具调用了。剩下的就是匹配主题的样式