Output single post custom taxonomy child terms

Question

I'm trying to output links to custom taxonomy assigned to a single post on a single post page. I've tried other thing but get errors. This is the closest I can get. It just needs to find the terms for the current post instead of outputting all terms of a taxonomy.

<?php
    $term_id = 6;
    $taxonomy_name = 'categories';
    $termchildren = get_term_children( $term_id, $taxonomy_name );
        foreach ( $termchildren as $child ) {
        $term = get_term_by( 'id', $child, $taxonomy_name );
        echo '<a href="' . get_term_link( $child, $taxonomy_name ) . '">' . $term->name . '</a> ';
    }
    ?>

@Howdy_McGee I tried the following code, where 'adoption-status' is a term for the custom taxonomy 'categories'. I'm looking for children of 'adoption-status'. It doesn't output anything. No errors either.

<?php get_the_terms( $post->ID, 'adoption-status' ); ?>

The following code almost works but displays all 'categories' of the current post, not just those of the term (or sub-category) 'adoption-status'

<?php echo get_the_term_list( $post->ID, 'categories', '', '', '' );?>

Answer 1

I hope I understand your question. You are looking for all terms connected to a single post, but only terms that are children to the adoption-status term

To get all the terms from a specific post, you can make use of wp_get_post_terms(). This will return all the terms of a specific taxonomy connected to the post.

You will also need to make use of get_term_children() to get all the child terms from your adoption-status term

Once you have all that, it is simply to compare the two, and only returning the terms that are associated with the post and is a child term to your given term.

You can try something like the following (NOTE: Change the term ids and taxonomy names accordingly)

$child_terms = get_term_children(21, 'category');
$all_terms   = wp_get_post_terms($post->ID, 'category');

foreach ( $all_terms as $term ) {

    if( !in_array($term->term_id, $child_terms ) ) 
        continue;

    echo $term->name;

}