WooCommerce: Add random product sorting option to shop / archives

sv-wc-random-product-sorting.php

<?php // only copy if needed

/**
 * Adds randomized product sorting option to WooCommerce stores (WC 2.3+)
 *
 * @param array $sortby the orderby options for product sorting
 * @return array - updated sorting options
 */
function sv_random_woocommerce_catalog_orderby( $sortby ) {
    $sortby['rand'] = __( 'Sort by: random order', 'my-textdomain' );
    return $sortby;
}
add_filter( 'woocommerce_catalog_orderby', 'sv_random_woocommerce_catalog_orderby' );
add_filter( 'woocommerce_default_catalog_orderby_options', 'sv_random_woocommerce_catalog_orderby' );