Mirroring Taxonomy Terms as Sub Terms to Another Taxonomy in WordPress

First off, don’t do this (also, say that post title 10 times fast; r/titlegore).
It’s better to not have to write logic into an app so that two things can see the same data from different parts of the db. It should be stored only in one spot and referenced from there. However, within a framework, when you’re using plugins whose code you’re not familiar with, sometimes it’s the way of least resistance. At first anyways, I suppose it depends on how complicated it is.

Now that’s out of the way, let me get to my weak excuses.

I needed to set up multi-taxonomy sort ordering. I need the sorting to be drag and drop, and it needs to automatically create the UI based on what terms are in the taxonomy. I haven’t been able to find a plugin which does all of this. I use one which allows for single taxonomy sorting and it hit’s all the other buttons. But I don’t know the plugin code well and I don’t currently have the time to do so.

I found another which can do multi-taxonomy sorting but it’s UI could be confusing for my clients and you need to manually set up the sorting UI’s. So, each time they add or remove a term they’d need to remove/add a set of options for that term. Not gonna happen.

My roundabout choice was to use the first mentioned plugin and mirror one of the taxonomies as sub categories to another.

Practically speaking in my context I have a custom post type, Projects (each project represents a spot/video), a Talent taxonomy (list of people’s names) and a Spot Type taxonomy (subjects for videos the”Talent” edit). The taxonomies are registered with the custom post type.

I’m mirroring the Spot Types terms to the Talent taxonomy as child categories/terms. I’m doing this because I don’t want to have the clients need to individually add the sub categories for each talent taxonomy term; there will be a lot. The code I wrote will take in two taxonomies; the taxonomy to mirror and the taxonomy to mirror to. On plugin activation all the terms in the TAXONOMY_TO_MIRROR_NAME will be added as sub terms to each of the TAXONOMY_TO_MIRROR_TO_NAME top level terms (aka, term->parent === 0). They will subsequently be created, updated, and deleted when any of the TAXONOMY_TO_MIRROR_NAME terms are (all together now) created, updated, and deleted.

The plugin still needs a proper going through, but if you need something like this here is a place to test and start.

There is a repository.

 

<?php

 namespace ThisBailiwick\TaxonomyMirror;
 /*
 Plugin Name: Taxonomy Mirror Sync
 */
 const PLUGIN_PREFIX = 'tx_mirror_';
 const OPTION_NAME = 'tb_mirrored_sub_category_ids';
 const TAXONOMY_TO_MIRROR_NAME = 'spot-categories';
 const TAXONOMY_TO_MIRROR_TO_NAME = 'talent-categories';


 register_activation_hook(__FILE__, __NAMESPACE__ . '\\activate');
 register_deactivation_hook(__FILE__, __NAMESPACE__ . '\\deactivate');

 add_action('edit_term', __NAMESPACE__ . '\\sync_categories_edit', 10, 3);
 add_action('created_term', __NAMESPACE__ . '\\sync_categories_create', 10, 3);
 add_action('delete_term', __NAMESPACE__ . '\\sync_categories_delete', 10, 5);

 /**
    *
    */
 function deactivate() {
    // delete sub term mirror option
    delete_option(OPTION_NAME);
 }

 /**
    * Does initial mirroring of all terms from TAXONOMY_TO_MIRROR_NAME to TAXONOMY_TO_MIRROR_TO_NAME.
    */
 function activate() {
    // get the saved sub term mirror values
    $mirrored_sub_category_ids = get_option(OPTION_NAME);

    if ($mirrored_sub_category_ids === false) {
     // we need to add the sub term mirror to the db
     // create values
     // get the spot category terms
     $taxonomy_to_mirror_terms = get_taxonomy_terms(TAXONOMY_TO_MIRROR_NAME);
     $new_mirrored_sub_category_ids = array();
     foreach ($taxonomy_to_mirror_terms as $to_mirror_term) {
        // now we add the sub terms to the top level terms of the taxonomy we are mirroring to
        $taxonomy_to_mirror_to_terms = get_taxonomy_terms(TAXONOMY_TO_MIRROR_TO_NAME);
        foreach ($taxonomy_to_mirror_to_terms as $to_mirror_to_term) {
         if ($to_mirror_to_term->parent === 0) {
            $new_term_ids = wp_insert_term($to_mirror_term->name, TAXONOMY_TO_MIRROR_TO_NAME, array('parent' => $to_mirror_to_term->term_id, 'slug' => $to_mirror_term->name . '-' . $to_mirror_to_term->name));
            if (!isset($new_term_ids->errors)) {
             $new_mirrored_sub_category_ids[$to_mirror_term->term_id][] = $new_term_ids['term_id'];
            } else {
             $new_mirrored_sub_category_ids[$to_mirror_term->term_id][] = $new_term_ids->error_data['term_exists'];
            }
         }
        }
     }

     // todo: why are we saving to the options table?
     add_option(OPTION_NAME, $new_mirrored_sub_category_ids);
    }
 }


 /**
    * When a term name or slug from the TAXONOMY_TO_MIRROR_NAME is edited this will check all of the TAXONOMY_TO_MIRROR_TO_NAME sub terms to make changes.
    * @param $term_id
    * @param $tt_id
    * @param $taxonomy
    */
 function sync_categories_edit($term_id, $tt_id, $taxonomy) {
    if ($taxonomy === TAXONOMY_TO_MIRROR_NAME) {
     $mirrored_sub_term_ids = get_option(OPTION_NAME);
     // get saving term values
     $saving_term = $_POST;

     // if the saving term id has a matching term id in the cached values, then compare the name and slug to see if either has changed
     $cached_values_for_term = $GLOBALS['wp_object_cache']->cache['terms'][$term_id];
     if (!empty($cached_values_for_term)) {
        $name_changed = false;
        $slug_changed = false;
        if ($cached_values_for_term->name !== $saving_term['name']) {
         // name changed
         $name_changed = true;
        }

        $parent_slug = get_term($cached_values_for_term->parent, TAXONOMY_TO_MIRROR_TO_NAME)->slug;

        // compare the cached value (what amounts to the mirror to taxonomy) trimmed of the postfix-ed parent-category name to the saving terms slug (taxonomy to mirror)
        if (str_replace('-' . $parent_slug, '', $cached_values_for_term->slug) !== $saving_term['slug']) {
         // slug changed
         $slug_changed = true;
        }

        // if either has changed then
        // loop through sub term mirror array at the id of the changing term and update within those terms whatever has changed for the spot category
        if ($name_changed === true || $slug_changed === true) {
         foreach ($mirrored_sub_term_ids[$saving_term['tax_ID']] as $sub_term_id) {
            // lazy blanket set the term name and slug
            if ($name_changed === true) {
             wp_update_term($sub_term_id, TAXONOMY_TO_MIRROR_TO_NAME, array(
                 'name' => $saving_term['name']
             ));
            }

            if ($slug_changed === true) {
             // need to postfix the taxonomy to mirror to parent name to slug
             $parent_slug = get_term(get_term($sub_term_id, TAXONOMY_TO_MIRROR_TO_NAME)->parent, TAXONOMY_TO_MIRROR_TO_NAME)->slug;
             wp_update_term($sub_term_id, TAXONOMY_TO_MIRROR_TO_NAME, array(
                 'slug' => $saving_term['slug'] . '-' . $parent_slug
             ));
            }
         }
        }
     }
    }
 }

 /**
    * When a new term is added to TAXONOMY_TO_MIRROR_NAME this will mirror the term to all TAXONOMY_TO_MIRROR_TO_NAME top lever terms as sub terms
    * @param $term_id
    * @param $tt_id
    * @param $taxonomy
    */
 function sync_categories_create($term_id, $tt_id, $taxonomy) {
    if ($taxonomy === TAXONOMY_TO_MIRROR_NAME) {
     // add new term as sub categories to all
     $saving_term_name = $_POST['tag-name'];
     $saving_term_slug = get_term_by('name', $_POST['tag-name'], 'spot-categories')->slug;
     $taxonomy_to_mirror_to_terms = get_taxonomy_terms(TAXONOMY_TO_MIRROR_TO_NAME);
     $mirror_term_values_to_update = array();
     foreach ($taxonomy_to_mirror_to_terms as $term) {
        if ($term->parent === 0) {
         // add the new term to the parent term
         $new_term_ids = wp_insert_term($saving_term_name, TAXONOMY_TO_MIRROR_TO_NAME, array('parent' => $term->term_id, 'slug' => $saving_term_slug . '-' . $term->name));
         $mirror_term_values_to_update[] = $new_term_ids['term_id'];
        }
     }

     // get current mirror term values
     $mirrored_sub_term_ids = get_option(OPTION_NAME);
     // add the new term values to them
     $mirrored_sub_term_ids[$term_id] = $mirror_term_values_to_update;
     //save the new value
     update_option(OPTION_NAME, $mirrored_sub_term_ids);
    }
 }

 /**
    * When a term from TAXONOMY_TO_MIRROR_NAME is deleted this will loop through all TAXONOMY_TO_MIRROR_TO_NAME terms and delete the relevant sub terms
    * todo: does this delete the term associations to the post object?
    * @param $term_id
    * @param $tt_id
    * @param $taxonomy
    * @param $deleted_term
    * @param $object_ids
    */
 function sync_categories_delete($term_id, $tt_id, $taxonomy, $deleted_term, $object_ids) {
    if ($taxonomy === TAXONOMY_TO_MIRROR_NAME) {
     // get current mirror term values
     $mirrored_sub_term_ids = get_option(OPTION_NAME);
     // remove all terms with ids which are in saved sub term mirror where the index is matching the id of the deleted term
     // loop through at the index which matches the id of the deleted term
     foreach ($mirrored_sub_term_ids[$term_id] as $sub_term_id) {
        //delete em' from the actual sub terms
        wp_delete_term($sub_term_id, TAXONOMY_TO_MIRROR_TO_NAME);
     }
     // delete em' from the sub term mirror array
     unset($mirrored_sub_term_ids[$term_id]);
     //save the new value to options in db
     update_option(OPTION_NAME, $mirrored_sub_term_ids);
    }

 }

 /**
    * @param $taxonomy_name
    * @param $return_ids - default 'all', other options can be found: http://developer.wordpress.org/reference/classes/wp_term_query/__construct/
    * @return array|int|\WP_Error
    */
 function get_taxonomy_terms($taxonomy_name, $return_ids = 'all') {

    $terms_args = array(
        'taxonomy' => $taxonomy_name,
        'fields' => $return_ids,
        'hide_empty' => false
    );
    // get the talent category terms
    $terms = get_terms($terms_args);
    return $terms;
 }

 

References
A helpful plugin for a confusing UI: Categories in Hierarchical Order | WordPress.org

https://github.com/ronalfy/reorder-by-term
Function Reference/add option « WordPress Codex
get_option() | Function | WordPress Developer Resources
Function Reference/update option « WordPress CodexWP_Term_Query::__construct() | Method | WordPress Developer Resources
Categories in Hierarchical Order | WordPress.org

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