WordPress | Get Child Terms

child_terms.php

<?php
function get_child_terms ( $term, $tax ) {
    $child_terms = array();
    if( $term && $tax ) {
        $the_term = get_term_by( 'slug', $term, $tax ); // Get term object using the slug
        $terms = get_the_terms(get_the_ID(), $tax); // Get the terms attached to the post
        if( $the_term && $terms ) {
            foreach ( $terms as $term ) {
                if( $the_term->term_id == $term->parent ) {
                    $child_terms[] = $term->name; // Only get the terms where the parent is the current term
                }
            }
        }
    }
    return $child_terms;
}
?>

Child Terms

Pass in the slug of the parent term and the slug of the taxonomy it belongs to and you will be rewarded with an array of child terms that belong to the parent term and have been assigned to that post.

Will return an empty array if none exist, so typical use would look like:

$child_terms = get_child_terms( 'extreme', 'sports' );
if( !empty( $child_terms ) ) {
    $child_terms_list = implode(', ', $child_terms);
}

Output example:

Skateboarding, Snowboarding, Rock Climbing