在正确的工具区域内显示你创建的WordPress小工具

<?php
function tutsplus_check_for_page_tree() {

    //首先检测当前访问的是否是一个页面
    if( is_page() ) {

        global $post;

        // 接着检测该页面是否有父级页面
        if ( $post->post_parent ){

            // 获取父级页面名单
            $parents = array_reverse( get_post_ancestors( $post->ID ) );

            // 获取最顶级页面
            return $parents[0];

        }

        // 返回ID  - 如果存在父级页面，就返回最顶级的页面ID，否则返回当前页面ID, or the current page if not
        return $post->ID;

    }

}
?>

function widget( $args, $instance ) {

    extract( $args );
    echo $before_widget;        
    echo $before_title . 'In this section:' . $after_title; 

}

function widget( $args, $instance ) {

    // kick things off
    extract( $args );
    echo $before_widget;        
    echo $before_title . 'In this section:' . $after_title;     

    // run a query if on a page
    if ( is_page() ) {

        // run the tutsplus_check_for_page_tree function to fetch top level page
        $ancestor = tutsplus_check_for_page_tree();

        // set the arguments for children of the ancestor page
        $args = array(
            'child_of' => $ancestor,
            'depth' => $instance[ 'depth' ],
            'title_li' => '',
        );

        // set a value for get_pages to check if it's empty
        $list_pages = get_pages( $args );

        // check if $list_pages has values
        if( $list_pages ) {

            // open a list with the ancestor page at the top
            ?>
            <ul class="page-tree">
                <?php // list ancestor page ?>
                <li class="ancestor">
                    <a href="<?php echo get_permalink( $ancestor ); ?>"><?php echo get_the_title( $ancestor ); ?></a>
                </li>

                <?php
                // use wp_list_pages to list subpages of ancestor or current page
                wp_list_pages( $args );;


            // close the page-tree list
            ?>
            </ul>

        <?php
        }
    }


}

<?php 
/*Plugin Name: List Subpages Widget
Description: This widget checks if the current page has parent or child pages and if so, outputs a list of the highest ancestor page and its descendants. This file supports part 5 of the series to create the widget and doesn't give you a functioning widget.
Version: 0.5
Author: Rachel McCollin
Author URI: http://rachelmccollin.com
License: GPLv2
*/
?>
<?php
?>
<?php
/*******************************************************************************
function tutsplus_check_for_page_tree() - checks if the current page is in a page tree.
*******************************************************************************/
?>
<?php
function tutsplus_check_for_page_tree() {

    //start by checking if we're on a page
    if( is_page() ) {

        global $post;

        // next check if the page has parents
        if ( $post->post_parent ){

            // fetch the list of ancestors
            $parents = array_reverse( get_post_ancestors( $post->ID ) );

            // get the top level ancestor
            return $parents[0];

        }

        // return the id  - this will be the topmost ancestor if there is one, or the current page if not
        return $post->ID;

    }

}
?>
<?php
class Tutsplus_List_Pages_Widget extends WP_Widget {

    function __construct() {

        parent::__construct(

            // base ID of the widget
            'tutsplus_list_pages_widget',

            // name of the widget
            __('List Related Pages', 'tutsplus' ),

            // widget options
            array (
                'description' => __( 'Identifies where the current page is in the site structure and displays a list of pages in the same section of the site. Only works on Pages.', 'tutsplus' )
            )

        );

    }

    function form( $instance ) {

        $defaults = array(
            'depth' => '-1'
        );
        $depth = $instance[ 'depth' ];

        // markup for form ?>
        <p>
            <label for="<?php echo $this->get_field_id( 'depth' ); ?>">Depth of list:</label>
            <input class="widefat" type="text" id="<?php echo $this->get_field_id( 'depth' ); ?>" name="<?php echo $this->get_field_name( 'depth' ); ?>" value="<?php echo esc_attr( $depth ); ?>">
        </p>

    <?php
    }

    function update( $new_instance, $old_instance ) {

        $instance = $old_instance;
        $instance[ 'depth' ] = strip_tags( $new_instance[ 'depth' ] );
        return $instance;

    }

    function widget( $args, $instance ) {

        // kick things off
        extract( $args );
        echo $before_widget;        
        echo $before_title . 'In this section:' . $after_title;     

        // run a query if on a page
        if ( is_page() ) {

            // run the tutsplus_check_for_page_tree function to fetch top level page
            $ancestor = tutsplus_check_for_page_tree();

            // set the arguments for children of the ancestor page
            $args = array(
                'child_of' => $ancestor,
                'depth' => $instance[ 'depth' ],
                'title_li' => '',
            );

            // set a value for get_pages to check if it's empty
            $list_pages = get_pages( $args );

            // check if $list_pages has values
            if( $list_pages ) {

                // open a list with the ancestor page at the top
                ?>
                <ul class="page-tree">
                    <?php // list ancestor page ?>
                    <li class="ancestor">
                        <a href="<?php echo get_permalink( $ancestor ); ?>"><?php echo get_the_title( $ancestor ); ?></a>
                    </li>

                    <?php
                    // use wp_list_pages to list subpages of ancestor or current page
                    wp_list_pages( $args );;


                // close the page-tree list
                ?>
                </ul>

            <?php
            }
        }


    }

}
?>
<?php
/*******************************************************************************
function tutsplus_register_list_pages_widget() - registers the widget.
*******************************************************************************/
?>
<?php
function tutsplus_register_list_pages_widget() {

    register_widget( 'Tutsplus_List_Pages_Widget' );

}
add_action( 'widgets_init', 'tutsplus_register_list_pages_widget' );
?>