WooCommerce - Allow sorting category archives by title, ascending and descending.

wc-sort-by-title.php

<?php
/*
Plugin Name: Sort WooCommerce archives by title
Plugin URI: https://www.facebook.com/groups/advanced.woocommerce/permalink/1931386533542423/
Description: Request on Facebook Advanced WooCommerce group - how to sort by title.
Author: Damien Carbery
Version: 0.1
*/

add_filter( 'woocommerce_default_catalog_orderby_options', 'swat_sort_by_title' );  // Add options to WooCommerce/Settings/Products/Display
add_filter( 'woocommerce_catalog_orderby', 'swat_sort_by_title' );  // Add options to sort dropdown on category page.
function swat_sort_by_title( $orderby_array ) {
	$orderby_array[ 'title' ] = 'Sort by title (A-Z)';
	$orderby_array[ 'title-desc' ] = 'Sort by title (Z-A)';

	return $orderby_array;
}