WordPress - Setting a custom post type default category(taxonomy term) using parameters

Question

I multiple custom post types and I would like to set a default category that can be set from one function through parameters. I initially did this for one custom post type and was hardcoded but I thought I'd make so we only have to output the function with parameters in case we ever decided to add more custom post types.

The problem is inside the function WordPress doesn't seem to link it's own hooks and functions and is returning invalid taxonomy errors when trying to set it via the wp_set_object_terms() function. When I have done this the WordPress way which would make you create a separate function for each post type and default term you want which I have put below.

function set_default_object_terms( $post_id, $post ) {
        if ( 'publish' === $post->post_status && $post->post_type === 'comic' ) {
            $defaults = array(
                'story' => array( 'draft' )https://silentcomics.com
                );
            $taxonomies = get_object_taxonomies( $post->post_type );
            foreach ( (array) $taxonomies as $taxonomy ) {
                $terms = wp_get_post_terms( $post_id, $taxonomy );
                if ( empty( $terms ) && array_key_exists( $taxonomy, $defaults ) ) {
                    wp_set_object_terms( $post_id, $defaults[$taxonomy], $taxonomy );
                }
            }
        }
    }
    add_action( 'save_post', 'set_default_object_terms', 0, 2 );

What I am trying to achieve is something like below but none of WordPress' global variables are working or any wordpress function like get_object_taxonomies() or wp_set_object_terms() which are used in the example WordPress gives.

Below is a simplified version of what I am trying to achieve and the parameters I am trying to pass through is the cpt slug, the taxonomy slug and the id of the category I want to fallback to. I have also tried it with the variable $cat_id as an array.

function set_default_term( $cpt_slug, $taxonomy_slug, $term_id ) {
    if ( isset( $_GET['post'] ) ) {
        $post_id   = intval( $_GET['post'] );
        $post_type = get_post_type( $post_id );
        $status    = get_post_status( $post_id );
        $cat_id    = array( $term_id );
        $cat_id    = array_map( 'intval', $cat_id );
        $cat_id    = array_unique( $cat_id );
        if ( $status === 'publish' && $post_type === $cpt_slug ) {
            wp_set_object_terms( $post_id, $cat_id, $taxonomy_slug, true );
        }
    }
}

add_action( 'save_post', 'set_default_term', 20, 3 );

set_default_term('deployment-guides', 'deployment-guide-category', 98);

your words none of WordPress' global variables are working or any wordpress function makes me think that you are trying to write this code as ajax handler in separate php file, and requesting this file directly from ajax. Am i right? If so you need to setup wp ajax handler in WP way and not as separate file with direct ajax call, because WP core isn't gets loaded if you do so, and wp functions are not accessible. — Mikhail.root

Mikhail.root Mikhail.root · Accepted Answer · 2020-03-16T10:08:06

Hi Brad i've checked your code just replaced post type to post and taxonomy to post_tag just to test general principle and it works well. See below a little modified code i've used to check.

function my_custom_set_default_terms_for_posts( $post_ID, $post ) {

    if ( 'publish' === $post->post_status && 'post' === $post->post_type ) {
        $defaults   = array(
            'post_tag' => array( 'example-default-tag-slug' ),
        );
        $taxonomies = get_object_taxonomies( $post->post_type );
        foreach ( (array) $taxonomies as $taxonomy ) {
            $terms = wp_get_post_terms( $post_ID, $taxonomy );
            if ( empty( $terms ) && array_key_exists( $taxonomy, $defaults ) ) {

                $terms_to_attach = $defaults[ $taxonomy ];

                if ( count( $terms_to_attach ) ) {
                    wp_set_object_terms( $post_ID, $terms_to_attach, $taxonomy );
                }
            }
        }
    }
}

add_action( 'save_post', 'my_custom_set_default_terms_for_posts', 0, 2 );

And thinking more about actual issue returning invalid taxonomy errors when trying to set it via the wp_set_object_terms() it might happened not because of your save_post handler does something wrong - it's a good right code.

You need to check how you initialize taxonomy and Custom Post Type (CPT), ideally you should do it on init hook so your CPT and custom taxonomies got initialized before this save_post hook or other code runs which relies on taxonomies\cpt existence.

Also when you initialize CPT and bound to it taxonomy, you need to initialize CPT first via register_post_type() and then initialize taxonomy which is bound to it via register_taxonomy(), as normally when you register taxonomy it expects an array of Post types to be used with, and they needs to be registered before registering taxonomy.

WordPress - Setting a custom post type default category(taxonomy term) using parameters

1 Answers