Attach posts based on category and position - Wordpress - php

Question

I'm working with a wordpress site where posts havn't been attached correctly, visibly it makes sense and all posts are in order but in the database there is no reference of any post connection. There are thousands of posts here, so I'll just show an example of what I'm working with, and what I would like to achieve via an action hook, or function. Or even just an update_post method.
Example list of posts currently
Post Title 1 (Category = Folder)
Post Title 2 (Category = Item)
Post Title 3 (Category = Item)
Post Title 4 (Category = Item)
Post Title 5 (Category = Item)
Post Title 6 (Category = Folder)
Post Title 7 (Category = Item)
Post Title 8 (Category = Item)
Post Title 9 (Category = Item)
Post Title 10 (Category = Item)
What I would like to achieve is:
Any posts in category 'item' that are below a post in category 'folder' to then become children of the above Folder post, so my posts would become something like this:
Post Title 1 (Category = Folder)
- Post Title 2 (Category = Item Post_parent = Post Title 1)
- Post Title 3 (Category = Item Post_parent = Post Title 1)
- Post Title 4 (Category = Item Post_parent = Post Title 1)
- Post Title 5 (Category = Item Post_parent = Post Title 1)
Post Title 6 (Category: Folder)
- Post Title 7 (Category = Item Post_parent = Post Title 6)
- Post Title 8 (Category = Item Post_parent = Post Title 6)
- Post Title 9 (Category = Item Post_parent = Post Title 6)
- Post Title 10 (Category = Item Post_parent = Post Title 6)
I'm wondering if someone can just put me on the right track of how I could do this writing a script myself. Something along the lines of:
For each post in category link > that is below a post in category folder > make this post a child of post in folder category above
What I am struggling to reference is the 'that is a below a post'. Could this be referenced by using published post date?

Answer 1

First of all, wordpresss post aren't hierarchical so you might want to eanble hierarchy support so you can see them on the back-end, you can add something like this
add_action('registered_post_type', '_enable_post_hierarchy', 10, 2 );
function _enable_post_hierarchy( $post_type ) {
if ($post_type !== 'post') return;
global $wp_post_types;
$wp_post_types['post']->hierarchical = 1;
add_post_type_support( 'post', 'page-attributes' );
}
Regarding about your main concern, you can achieve what you want by;
First;
create custom WP_Query, query all the post (though I think you should implement paging as you have a lot of posts) with ITEM category and make sure the order is the same as what you stated above, I believe its orderby=date and order=DESC
Then;
After you get the results, loop through each result and do another query, this time, it must only need one result, with the category FOLDER and/or not in category ITEM, and the most important part is that the POST_DATE must be greater than the current item POST_DATE (from your loop ), you can either create custom SQL query or try using WP_Query
the other method is to use get_adjacent_post built-in function, this is use on wordpress next and previous post, though this won't work if you have other category than ITEM and FOLDER. check it out https://codex.wordpress.org/Function_Reference/get_adjacent_post
Here's some NOT FULLY tested code I've come up with
First lets try getting the data and displaying the array on the front-end to verify if our new data array is built properly
// spit the data to verify the order and hierarchy
add_action('wp_head', function() {
echo '<pre>', print_r( _check_data_post(), 1), '</pre>';
});
function _check_data_post( $display = 'data' ) {
// ID of the item category
$item_id = 29;
//create query argument
$args = [
'post_type' => 'post',
'post_status' => 'publish',
'orderby' => 'date',
'order' => 'DESC',
'cat' => $item_id,
// lets add some limit not to kill the server
'post_per_page' => 50,
];
//build new query
$q = new WP_Query( $args );
//get all query result
$posts = $q->get_posts();
//new data holder
$data = [];
// loop through each result
foreach ($posts as $key => $new_post) {
// the global $post is needed for get_adjacent_post to work
global $post;
// assign each result to $post
$post = $new_post;
// get the next post, the parameters is as follows
// false - must not be only in same terms, meaning its not gonna query in ITEM category only but rather query all category
// $item_id - exclude the specified ID, we must not include the ITEM category
// false - (true means previous) NEXT to the current $post which is the current item of our loop, meaning it must have greater date than our current item
// This will not work if you have categories other then Folder and Item
// You should write your own custom SQL to be more specific and adjust on your need
$parent = get_adjacent_post( false, $item_id , false );
if( $display == 'ids' ) {
// lets return each post ID with additional "parent" ID
$data[$key]['id'] = $post->ID;
$data[$key]['parent'] = $parent->ID;
} else {
// Display Title and Category instead of the ID to verify the result
$data[$key]['cat'] = get_the_category( $post->ID )[0]->name;
$data[$key]['title'] = $post->post_title;
$data[$key]['parent'] = [
'cat' => get_the_category( $parent->ID )[0]->name,
'title' => $parent->post_title,
];
}
}
return $data;
}
Once its verified, we will then loop through each item and update each item with new parent post ID, you can call this function somewhere safe and run only once, its also better to add a bunch of conditional verification and error messages
function _update_data_post() {
// get the all the item, must be IDs only
$list_items = _check_data_post('ids');
// loop through each item
foreach ( $list_items as $items ) {
//assign item data
$data = [
'ID' => $items['id'],
'post_parent' => $items['parent'],
];
//update item with assigning post_parent value
wp_update_post( $data );
}
}