wordpress: how to add hierarchy to posts

Question

I am creating a web-site on wordpress platform where I want to be able to post my own book texts. So what I want is to have a some kind of hierarchy where I would add a post and then add children to it (chapters). I found this:

register_post_type( 'post', array(
        'labels' => array(
            'name_admin_bar' => _x( 'Post', 'add new on admin bar' ),
        ),
        'public'  => true,
        '_builtin' => true, /* internal use only. don't use this when registering your own post type. */
        '_edit_link' => 'post.php?post=%d', /* internal use only. don't use this when registering your own post type. */
        'capability_type' => 'post',
        'map_meta_cap' => true,
        'hierarchical' => false,
        'rewrite' => false,
        'query_var' => false,
        'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'trackbacks', 'custom-fields', 'comments', 'revisions', 'post-formats' ),
    ) );

and tried to make the 'hierarchical"=>true, but there was no effect. Can anyone help?

Answer 1

best solution is to create custom taxonomy [1]: http://codex.wordpress.org/Function_Reference/register_taxonomy and create main slug - books or something else.

Answer 2

I came here looking to achieve:

1. Adding page attributes to post_type posts to add parent posts
2. Being able to add a page template to post_type posts
3. Being able to get hierarchical permalink structure on post_type posts

I was able to use the accepted answer to accomplish 1 & 2, but not 3.

Note: to fully get 2 to work, you need to specify the post_type in the template comments of your page template like this:

<?php
/*
Template Name: Your Post Template Name
Template Post Type: post
*/

For 3, I found a plugin that ruined my post_type pages, and it was a lot of pretty awful, unmaintained code.

So I wrote a solution to accomplish all this, borrowing from this answer:

(Tested with 4.9.8)

<?php

add_action('registered_post_type', 'make_posts_hierarchical', 10, 2 );

// Runs after each post type is registered
function make_posts_hierarchical($post_type, $pto){

    // Return, if not post type posts
    if ($post_type != 'post') return;

    // access $wp_post_types global variable
    global $wp_post_types;

    // Set post type "post" to be hierarchical
    $wp_post_types['post']->hierarchical = 1;

    // Add page attributes to post backend
    // This adds the box to set up parent and menu order on edit posts.
    add_post_type_support( 'post', 'page-attributes' );

}

/**
 * Get parent post slug
 * 
 * Helpful function to get the post name of a posts parent
 */
function get_parent_post_slug($post) {
  if (!is_object($post) || !$post->post_parent) {
    return false;
  }

  return get_post($post->post_parent)->post_name;
}

/**
 * 
 * Edit View of Permalink
 * 
 * This affects editing permalinks, and $permalink is an array [template, replacement]
 * where replacement is the post_name and template has %postname% in it.
 * 
 **/
add_filter('get_sample_permalink', function($permalink, $post_id, $title, $name, $post) {
  if ($post->post_type != 'post' || !$post->post_parent) {
    return $permalink;
  }

  // Deconstruct the permalink parts
  $template_permalink = current($permalink);
  $replacement_permalink = next($permalink);

  // Find string
  $postname_string = '/%postname%/';

  // Get parent post
  $parent_slug = get_parent_post_slug($post);

  $altered_template_with_parent_slug = '/' . $parent_slug . $postname_string;
  $new_template = str_replace($postname_string, $altered_template_with_parent_slug, $template_permalink);

  $new_permalink = [$new_template, $replacement_permalink];

  return $new_permalink;
}, 99, 5);

/**
 * Alter the link to the post
 * 
 * This affects get_permalink, the_permalink etc. 
 * This will be the target of the edit permalink link too.
 * 
 * Note: only fires on "post" post types.
 */
add_filter('post_link', function($post_link, $post, $leavename){

  if ($post->post_type != 'post' || !$post->post_parent) {
    return $post_link;
  }

  $parent_slug = get_parent_post_slug($post);
  $new_post_link = str_replace($post->post_name, $parent_slug . '/' . $post->post_name, $post_link);

  return $new_post_link;
}, 99, 3);

/**
 * Before getting posts
 * 
 * Has to do with routing... adjusts the main query settings
 * 
 */
add_action('pre_get_posts', function($query){
  global $wpdb, $wp_query;

  $original_query = $query;
  $uri = $_SERVER['REQUEST_URI'];

  // Do not do this post check all the time
  if ( $query->is_main_query() && !is_admin()) {

    // get the post_name
    $basename = basename($uri);
    // find out if we have a post that matches this post_name
    $test_query = sprintf("select * from $wpdb->posts where post_type = '%s' and post_name = '%s';", 'post', $basename);
    $result = $wpdb->get_results($test_query);

    // if no match, return default query, or if there's no parent post, this is not necessary
    if (!($post = current($result)) || !$post->post_parent) {
      return $original_query;
    }

    // get the parent slug
    $parent_slug = get_parent_post_slug($post);
    // concat the parent slug with the post_name to get most of the url
    $hierarchal_slug = $parent_slug . '/' . $post->post_name;

    // if the concat of parent-slug/post-name is not in the uri, this is not the right post.
    if (!stristr($uri, $hierarchal_slug)) {
      return $original_query;
    }

    // pretty high confidence that we need to override the query.
    $query->parse_query( [ 'post_type'=> ['post'] ] );
    $query->is_home     = false; 
    $query->is_page     = true;  
    $query->is_single   = true; 
    $query->queried_object_id = $post->ID;  
    $query->set('page_id', $post->ID);

    return $query;
  }


}, 1);

You can save this to a file custom-posts-hierarchy.php and include it in your functions.php file in your theme, or you can add to the top:

/*
Plugin Name: Custom Posts Hierarchy
Plugin URI:
Description: Add page attributes to posts and support hiearchichal
Author: Angela Murrell
Version:
Author URI: 
*/

And drop it into your plugins folder. Good luck!