is_child_term()

is-child-term.php

// is_child_term()
// -------------------------------------------------------------
function is_child_term($taxonomy, $parent_id){
	$child_terms = get_term_children( $parent_id, $taxonomy );
	$response = false;
	
	foreach ( $child_terms as $term ):
		if(is_tax($taxonomy, $term)):
			$response = true;
		endif;
	endforeach;
	
	return $response;
}

This snippet adds to the plethora of Conditional Tags that WordPress already has, but for some reason doesn't have this one.

Put simply, this function works much like is_tax(), but checks whether the current taxonomy term is a child of a specific taxonomy term. It's to be used within taxonomy-[name].php file, so you can tweak the layout within without creating separate theme files (taxonomy-[name]_[term].php). You'll most likely use it alongside is_tax().

I needed this because I needed to supply a completely different looking loop for a Videos section, and any of its sub terms.

if(is_tax( 'type', 10) || is_child_term('type', 10)):
    // loop for 'Videos' and sub terms
else:
    // loop for every other taxonomy term
endif;