[Wordpress] Get the term names of a post

functions.php

/**
 * Retrieve a post's terms as a list with specified format.
 *
 * @since 2.5.0
 *
 * @param int $id Post ID.
 * @param string $taxonomy Taxonomy name.
 * @param string $before Optional. Before list.
 * @param string $sep Optional. Separate items using this.
 * @param string $after Optional. After list.
 * @return string
 */
function get_the_term_names( $id = 0, $taxonomy, $sep = '') {
    
	$terms = get_the_terms( $id, $taxonomy );

	if ( is_wp_error( $terms ) )
		return $terms;

	if ( empty( $terms ) )
		return false;

	foreach ( $terms as $term ) {
		$term_names[] = $term->name;
	}

	return join( $sep, $term_names ) ;
}