wordpress: how to add hierarchy to posts

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?

Solution

Here is my workaround. This achieves exactly what you want, to be able to set post parents for the builtin post type post. You can achieve this by adding an action to the registred_post_type action hook. Just add this to your theme's functions.php.

add_action('registered_post_type', 'igy2411_make_posts_hierarchical', 10, 2 );

// Runs after each post type is registered
function igy2411_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' );

}

There can be dozens of reasons why making posts hierarchical can be helpful. My use case is that the client wanted to structure their (already existing) posts into issues, where child posts are articles of one issue (parent posts).

This is easily achieved by limiting the query to only show posts that have no parents, using.

 'post_parent' => 0,

in your query $args.