如果想增加调用访客最近浏览过的文章功能，可以使用Last Viewed Posts这个插件，但由于这个插件很久没更新了，使用高版本的php及wordpress存在兼容性问题，可以按以下方式修改：

高版本的php不支持preg_replace，需要将

preg_replace('!s:(\d+):"(.*?)";!e', "'s:'.strlen('$2').':\"$2\";'", stripslashes($_COOKIE["WP-LastViewedPosts"]))

替换为：

preg_replace_callback('!s:(\d+):"(.*?)";!', function($m) { return 's:'.strlen($m[2]).":\"$m[2]\";";}, stripslashes($_COOKIE["WP-LastViewedPosts"]))

修改完之后后台添加时报“无效值”错误，可以将

add_action('widgets_init', 'zg_lwp_init');

及zg_lwp_init方法代码改为extends WP_Widget的方法来初始化小工具，代码如下：

class last_viewed_posts extends WP_Widget {    
    public function __construct() {    
        $widget_ops = array(    
                'classname' => 'recently_viewed',    
                'description' => __( 'Last Viewed Posts' ),    
                'customize_selective_refresh' => true,    
        );    
        parent::__construct('last_viewed_posts', 'Last Viewed Posts', $widget_ops);    
    }    
        
    function widget($args, $instance) {    
        extract($args);    
        $title = apply_filters( 'widget_title', $instance['title'] );    
            
        echo $before_widget;    
        if ( ! emptyempty( $title ) )    
            echo $before_title . $title . $after_title;    
            ?>    
    
<div class="post_cat">    
    <div id="recently-viewed">    
    <?php if (function_exists('zg_recently_viewed')) { ?>    
    <?php zg_recently_viewed(); ?>    
    <?php } ?>    
    </div>    
</div>    
    
<?php    
    echo $after_widget;    
    }    
    function update( $new_instance, $old_instance ) {    
        if (!isset($new_instance['submit'])) {    
            return false;    
        }    
            $instance = $old_instance;    
            $instance = array();    
            $instance['title'] = strip_tags( $new_instance['title'] );    
            return $instance;    
        }    
    function form($instance) {    
        if ( isset( $instance[ 'title' ] ) ) {    
            $title = $instance[ 'title' ];    
        }    
        else {    
            $title = 'Last Viewed Posts';    
        }    
?>    
    <p><label for="<?php echo $this->get_field_id( 'title' ); ?>">标题：</label>    
    <input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo $title; ?>" /></p>    
        
    <input type="hidden" id="<?php echo $this->get_field_id('submit'); ?>" name="<?php echo $this->get_field_name('submit'); ?>" value="1" />    
<?php }    
}    
add_action( 'widgets_init', create_function( '', 'register_widget( "last_viewed_posts" );' ) );