How best to store data (URLs and IDs) extracted from posts and pages using custom taxonomies

Question

I want to store metadata extracted from post/page content:

• IDs of other posts/pages on the same blog linked within the content of each post/page
• certain external URLs contained within the content of each post/page

I've created two custom taxonomies to store this information: internal_reference and external_reference. Both are non-hierarchical and non-public. Edit page meta-boxes are also switched off as the metadata is extracted programmatically, and I don't want users overriding this with the checkboxes provided for other taxonomies like categories.

I've written a function that can extract the IDs and URLs from the post/page content, which runs on the save_post hook.

The problem I'm having is how best to store this information. Clearly I must use wp_set_post_terms to associated the terms with the post in question, but I can't work out whether I need to use add_term_meta to set the IDs and URLs or if I can just use the term's name or slug field. If it's best to store this using term meta data, then how do I find out each newly created term's ID after I call wp_set_post_terms with a bunch of URLs or post IDs?

How is this sort of thing intended to be done in WordPress? Forgive me if this is a rather basic question, but this feature of WordPress is new to me.

Answer 1

Ah, I found it. I just need to give a unique name to each term (so for the external URLs, I named them url-[md5] where [md5] is the MD5 hash of the URL), and then call add_term_meta and set the necessary information, then add this term to the post using my custom taxonomies. For example, this is the working external term metadata setter:

foreach ( $external_urls as $url ) {
    $url = esc_url( $url );
    // don't use wp_hash here because it salts the data
    $term_name = "url-" . md5( $url );
    $terms[$term_name] = $url;
}

// update post's reference taxonomy terms (replaces any existing terms)
wp_set_post_terms( $post->ID, array_keys( $terms ), 'external_reference' );

// add metadata
foreach ( $terms as $term_name => $url ) {
    // get term
    $term = get_term_by( 'name', $term_name, 'external_reference' );
    // add URL as metadata for the term created above
    update_term_meta( $term->term_id, "url", $url );
}