やりたいこと

こんなカンジで各ページに手動でOrderをセットする

page1000 (order: 1000)
- page1001 (order: 1001)
- page1002 (order: 1002)
page2000 (order: 2000)

page1001を開くと、ページ下部に

<- page1000 page1002 ->

とページ送りが設置されている。

やる

いくつかのテーマをながめてみると、下記２つのファンクションで実装されていることがわかった。

previous_post_link(…)

next_post_link(…)

中を追っていくと、両方ともget_adjacent_post(…)を呼んでおり、うまいことfilterなるものを設定すれば挙動を変えられそうな気がする。

    /**
     * Filters the WHERE clause in the SQL for an adjacent post query.
     *
     * The dynamic portion of the hook name, `$adjacent`, refers to the type
     * of adjacency, 'next' or 'previous'.
     *
     * @since 2.5.0
     * @since 4.4.0 Added the `$taxonomy` and `$post` parameters.
     *
     * @param string $where          The `WHERE` clause in the SQL.
     * @param bool   $in_same_term   Whether post should be in a same taxonomy term.
     * @param array  $excluded_terms Array of excluded term IDs.
     * @param string $taxonomy       Taxonomy. Used to identify the term used when `$in_same_term` is true.
     * @param WP_Post $post           WP_Post object.
     */
    $where = apply_filters( "get_{$adjacent}_post_where", $wpdb->prepare( "WHERE p.post_date $op %s AND p.post_type = %s $where", $current_post_date, $post->post_type ), $in_same_term, $excluded_terms, $taxonomy, $post );
 
    /**
     * Filters the ORDER BY clause in the SQL for an adjacent post query.
     *
     * The dynamic portion of the hook name, `$adjacent`, refers to the type
     * of adjacency, 'next' or 'previous'.
     *
     * @since 2.5.0
     * @since 4.4.0 Added the `$post` parameter.
     *
     * @param string $order_by The `ORDER BY` clause in the SQL.
     * @param WP_Post $post    WP_Post object.
     */
    $sort  = apply_filters( "get_{$adjacent}_post_sort", "ORDER BY p.post_date $order LIMIT 1", $post );

/**

* Filters the WHERE clause in the SQL for an adjacent post query.

* The dynamic portion of the hook name, `$adjacent`, refers to the type

* of adjacency, 'next' or 'previous'.

* @since 2.5.0

* @since 4.4.0 Added the `$taxonomy` and `$post` parameters.

* @param string $where The `WHERE` clause in the SQL.

* @param bool $in_same_term Whether post should be in a same taxonomy term.

* @param array $excluded_terms Array of excluded term IDs.

* @param string $taxonomy Taxonomy. Used to identify the term used when `$in_same_term` is true.

* @param WP_Post $post WP_Post object.

$where = apply_filters( "get_{$adjacent}_post_where", $wpdb->prepare( "WHERE p.post_date $op %s AND p.post_type = %s $where", $current_post_date, $post->post_type ), $in_same_term, $excluded_terms, $taxonomy, $post );

/**

* Filters the ORDER BY clause in the SQL for an adjacent post query.

* The dynamic portion of the hook name, `$adjacent`, refers to the type

* of adjacency, 'next' or 'previous'.

* @since 2.5.0

* @since 4.4.0 Added the `$post` parameter.

* @param string $order_by The `ORDER BY` clause in the SQL.

* @param WP_Post $post WP_Post object.

$sort = apply_filters( "get_{$adjacent}_post_sort", "ORDER BY p.post_date $order LIMIT 1", $post );

テーマ hueman (3.3.2)の場合

注：get_adjacent_postの引数で$post（及び$taxonomy）が指定できるのはWordPress4.4.0から
なのでそれ以前はglobalのpostを使用する必要あり

Child Theme Configuratorというのを使って子テーマ(hueman-child)を作成

wp-content/themes/hueman-child
├── functions.php <- 自動で作成される。ここにフィルターを定義する。
├── page.php <- このテーマの固定ページにはページ送りが無いので、親テーマからコピーして変更
├── parts
│ └── post-nav.php <- 投稿の場合ここでページ送りを作成しているので、固定ページ用の処理を追加
├── screenshot.png
└── style.css

<?php
// Exit if accessed directly
if ( !defined( 'ABSPATH' ) ) exit;

// BEGIN ENQUEUE PARENT ACTION
// AUTO GENERATED - Do not modify or remove comment markers above or below:

function get_previous_page_where( $where, $in_same_term, $excluded_terms, $taxonomy, $post) {
  global $wpdb;
  return $wpdb->prepare( "
    WHERE p.ID != %s
    AND p.post_parent = %s
    AND ( p.menu_order < %s
      OR p.menu_order = %s AND p.post_date < %s )
    AND p.post_type = %s
    AND p.post_status = 'publish'",
    $post->ID,
    $post->post_parent,
    $post->menu_order,
      $post->menu_order, $post->post_date,
    $post->post_type);
}

function get_next_page_where($where, $in_same_term, $excluded_terms, $taxonomy, $post) {
  global $wpdb;
  return $wpdb->prepare( "
    WHERE p.ID != %s
    AND p.post_parent = %s
    AND ( p.menu_order > %s
      OR p.menu_order = %s AND p.post_date > %s )
    AND p.post_type = %s
    AND p.post_status = 'publish'",
    $post->ID,
    $post->post_parent,
    $post->menu_order,
      $post->menu_order, $post->post_date,
    $post->post_type);
}

function get_previous_page_sort($sort, $post) {
  return "ORDER BY p.menu_order DESC, p.post_date DESC LIMIT 1";
}

function get_next_page_sort($sort, $post) {
  return "ORDER BY p.menu_order ASC, p.post_date ASC LIMIT 1";
}

// END ENQUEUE PARENT ACTION

<?php

// Exit if accessed directly

if ( !defined( 'ABSPATH' ) ) exit;

// BEGIN ENQUEUE PARENT ACTION

// AUTO GENERATED - Do not modify or remove comment markers above or below:

function get_previous_page_where( $where, $in_same_term, $excluded_terms, $taxonomy, $post) {

global $wpdb;

return $wpdb->prepare( "

WHERE p.ID != %s

AND p.post_parent = %s

AND ( p.menu_order < %s

OR p.menu_order = %s AND p.post_date < %s )

AND p.post_type = %s

AND p.post_status = 'publish'",

$post->ID,

$post->post_parent,

$post->menu_order,

$post->menu_order, $post->post_date,

$post->post_type);

}

function get_next_page_where($where, $in_same_term, $excluded_terms, $taxonomy, $post) {

global $wpdb;

return $wpdb->prepare( "

WHERE p.ID != %s

AND p.post_parent = %s

AND ( p.menu_order > %s

OR p.menu_order = %s AND p.post_date > %s )

AND p.post_type = %s

AND p.post_status = 'publish'",

$post->ID,

$post->post_parent,

$post->menu_order,

$post->menu_order, $post->post_date,

$post->post_type);

}

function get_previous_page_sort($sort, $post) {

return "ORDER BY p.menu_order DESC, p.post_date DESC LIMIT 1";

}

function get_next_page_sort($sort, $post) {

return "ORDER BY p.menu_order ASC, p.post_date ASC LIMIT 1";

}

// END ENQUEUE PARENT ACTION

実験として、同じ親ページを持つページだけを送りの対象にした。
（post_parentを指定）

<?php get_header(); ?>
<section class="content">
        <?php hu_get_template_part('parts/page-title'); ?>
        <div class="pad group">
                <?php while ( have_posts() ): the_post(); ?>
                        <article <?php post_class('group'); ?>>
                                <?php hu_get_template_part('parts/page-image'); ?>
                                <div class="entry themeform">
                                        <?php the_content(); ?>
                                        <div class="clear"></div>
                                </div><!--/.entry-->
                        </article>
                        <?php if ( hu_is_checked('page-comments') ) { comments_template('/comments.php',true); } ?>
                <?php endwhile; ?>
                <?php if ( 'content' == hu_get_option( 'post-nav' ) ) { get_template_part('parts/post-nav'); } ?>
        </div><!--/.pad-->
</section><!--/.content-->
<?php get_sidebar(); ?>
<?php get_footer(); ?>

<?php get_header(); ?>

<?php hu_get_template_part('parts/page-title'); ?>

<?php while ( have_posts() ): the_post(); ?>

<?php hu_get_template_part('parts/page-image'); ?>

<?php the_content(); ?>

</div>

</article>

<?php if ( hu_is_checked('page-comments') ) { comments_template('/comments.php',true); } ?>

<?php endwhile; ?>

<?php if ( 'content' == hu_get_option( 'post-nav' ) ) { get_template_part('parts/post-nav'); } ?>

</div>

</section>

<?php get_sidebar(); ?>

<?php get_footer(); ?>

13行目を追加

<?php if ( is_single() ): ?>
  <ul class="post-nav group">
    <li class="previous"><?php previous_post_link('%link', '<i class="fa fa-chevron-left"></i><strong>'.__('Previous story', 'hueman').'</strong> <span>%title</span>', true); ?></li>
    <li class="next"><?php next_post_link('%link', '<i class="fa fa-chevron-right"></i><strong>'.__('Next story', 'hueman').'</strong> <span>%title</span>', true); ?></li>
  </ul>
<?php elseif ( is_page() ): ?>
  <?php
    add_filter( 'get_previous_post_where', 'get_previous_page_where', 10, 5 );
    add_filter( 'get_previous_post_sort', 'get_previous_page_sort', 10, 2 );
    add_filter( 'get_next_post_where', 'get_next_page_where', 10, 5 );
    add_filter( 'get_next_post_sort', 'get_next_page_sort', 10, 2 );
  ?>
  <ul class="post-nav group">
    <li class="previous"><?php previous_post_link('%link', '<i class="fa fa-chevron-left"></i><strong>'.__('Previous story', 'hueman').'</strong> <span>%title</span>', false); ?></li>
    <li class="next"><?php next_post_link('%link', '<i class="fa fa-chevron-right"></i><strong>'.__('Next story', 'hueman').'</strong> <span>%title</span>', false); ?></li>
  </ul>
<?php endif; ?>

<?php if ( is_single() ): ?>

<li class="previous"><?php previous_post_link('%link', '<i class="fa fa-chevron-left"></i><strong>'.__('Previous story', 'hueman').'</strong> <span>%title</span>', true); ?></li>

<li class="next"><?php next_post_link('%link', '<i class="fa fa-chevron-right"></i><strong>'.__('Next story', 'hueman').'</strong> <span>%title</span>', true); ?></li>

</ul>

<?php elseif ( is_page() ): ?>

<?php

add_filter( 'get_previous_post_where', 'get_previous_page_where', 10, 5 );

add_filter( 'get_previous_post_sort', 'get_previous_page_sort', 10, 2 );

add_filter( 'get_next_post_where', 'get_next_page_where', 10, 5 );

add_filter( 'get_next_post_sort', 'get_next_page_sort', 10, 2 );

<li class="previous"><?php previous_post_link('%link', '<i class="fa fa-chevron-left"></i><strong>'.__('Previous story', 'hueman').'</strong> <span>%title</span>', false); ?></li>

<li class="next"><?php next_post_link('%link', '<i class="fa fa-chevron-right"></i><strong>'.__('Next story', 'hueman').'</strong> <span>%title</span>', false); ?></li>

</ul>

<?php endif; ?>

3, 4行目でxxx_post_linkのお尻の引数をtrueにした。（投稿のページ送りを同カテゴリーに制限）

6-16行目で固定ページ用のフィルターをセット

下記の用に表示
投稿ページ：同カテゴリー制限、投稿時刻昇順
固定ページ：同親ページ制限、Order(menu_order)昇順

テーマ customizr (3.4.36)の場合

注：get_adjacent_postの引数で$post（及び$taxonomy）が指定できるのはWordPress4.4.0から
なのでそれ以前はglobalのpostを使用する必要あり

customizrの場合、固定ページのページ送りがサポートされており、UIからオプションをONにする。

ただ、このままだと固定ページのソートが投稿時刻になっているので、Order(menu_order)に変更する。

さっきhuemanで実装した”投稿のページ送りを同カテゴリーに制限”について

Restrict the post navigation to the same category
を見るとtc_previous_single_post_link_args、tc_next_single_post_link_argsという引数を定義すると制御できるように書いてあるけど、呼び出し元のczr-front.phpで前後投稿の存在判定をこの引数と関係なく行っているので、下記のように空のボタンが表示されてしまう。
czr-front.phpは結構でかいファイルなのでいぢりたくない
同カテゴリーに縛らなくていい気がしてきた

ので、投稿ページはそのまま（同カテゴリー制限なし）、固定ページも同親ページ制限は実装せず、ソートのみOrder順に変更する。

Child Theme Configuratorというのを使って子テーマ(customizr-child)を作成

wp-content/themes/customizr-child
├── functions.php <- 自動で作成される。ここにフィルターを定義する。
├── screenshot.png
└── style.css

<?php
// Exit if accessed directly
if ( !defined( 'ABSPATH' ) ) exit;

// BEGIN ENQUEUE PARENT ACTION
// AUTO GENERATED - Do not modify or remove comment markers above or below:

add_filter('tc_show_post_navigation', 'add_filter_for_page');

function add_filter_for_page ( $post_nav_enabled ) {
  if ( is_page() ) {
    add_filter( 'get_previous_post_where', 'get_previous_page_where', 10, 5 );
    add_filter( 'get_previous_post_sort', 'get_previous_page_sort', 10, 2 );
    add_filter( 'get_next_post_where', 'get_next_page_where', 10, 5 );
    add_filter( 'get_next_post_sort', 'get_next_page_sort', 10, 2 );
  }
  return $post_nav_enabled;
}

function get_previous_page_where( $where, $in_same_term, $excluded_terms, $taxonomy, $post) {
  global $wpdb;
  return $wpdb->prepare( "
    WHERE p.ID != %s
    AND ( p.menu_order < %s
      OR p.menu_order = %s AND p.post_date < %s )
    AND p.post_type = %s
    AND p.post_status = 'publish'",
    $post->ID,
    $post->menu_order,
      $post->menu_order, $post->post_date,
    $post->post_type);
}

function get_next_page_where($where, $in_same_term, $excluded_terms, $taxonomy, $post) {
  global $wpdb;
  return $wpdb->prepare( "
    WHERE p.ID != %s
    AND ( p.menu_order > %s
      OR p.menu_order = %s AND p.post_date > %s )
    AND p.post_type = %s
    AND p.post_status = 'publish'",
    $post->ID,
    $post->menu_order,
      $post->menu_order, $post->post_date,
    $post->post_type);
}

function get_previous_page_sort($sort, $post) {
  return "ORDER BY p.menu_order DESC, p.post_date DESC LIMIT 1";
}

function get_next_page_sort($sort, $post) {
  return "ORDER BY p.menu_order ASC, p.post_date ASC LIMIT 1";
}

// END ENQUEUE PARENT ACTION

<?php

// Exit if accessed directly

if ( !defined( 'ABSPATH' ) ) exit;

// BEGIN ENQUEUE PARENT ACTION

// AUTO GENERATED - Do not modify or remove comment markers above or below:

add_filter('tc_show_post_navigation', 'add_filter_for_page');

function add_filter_for_page ( $post_nav_enabled ) {

if ( is_page() ) {

add_filter( 'get_previous_post_where', 'get_previous_page_where', 10, 5 );

add_filter( 'get_previous_post_sort', 'get_previous_page_sort', 10, 2 );

add_filter( 'get_next_post_where', 'get_next_page_where', 10, 5 );

add_filter( 'get_next_post_sort', 'get_next_page_sort', 10, 2 );

}

return $post_nav_enabled;

}

function get_previous_page_where( $where, $in_same_term, $excluded_terms, $taxonomy, $post) {

global $wpdb;

return $wpdb->prepare( "

WHERE p.ID != %s

AND ( p.menu_order < %s

OR p.menu_order = %s AND p.post_date < %s )

AND p.post_type = %s

AND p.post_status = 'publish'",

$post->ID,

$post->menu_order,

$post->menu_order, $post->post_date,

$post->post_type);

}

function get_next_page_where($where, $in_same_term, $excluded_terms, $taxonomy, $post) {

global $wpdb;

return $wpdb->prepare( "

WHERE p.ID != %s

AND ( p.menu_order > %s

OR p.menu_order = %s AND p.post_date > %s )

AND p.post_type = %s

AND p.post_status = 'publish'",

$post->ID,

$post->menu_order,

$post->menu_order, $post->post_date,

$post->post_type);

}

function get_previous_page_sort($sort, $post) {

return "ORDER BY p.menu_order DESC, p.post_date DESC LIMIT 1";

}

function get_next_page_sort($sort, $post) {

return "ORDER BY p.menu_order ASC, p.post_date ASC LIMIT 1";

}

// END ENQUEUE PARENT ACTION

8行目のtc_show_post_navigationは、czr-front.php内部のページ送り作成処理から呼び出してもらうため。

下記の用に表示
投稿ページ：投稿時刻昇順（デフォルトのまま）
固定ページ：Order(menu_order)昇順

WordPress 固定ページのページ送りをいぢる

やりたいこと

やる

テーマ hueman (3.3.2)の場合

テーマ customizr (3.4.36)の場合

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