Sorting Products by Custom Meta Fields
add_filter( 'woocommerce_shortcode_products_query', 'woocommerce_shortcode_products_orderby' );
function woocommerce_shortcode_products_orderby( $args ) {
$standard_array = array('menu_order','title','date','rand','id');
if( isset( $args['orderby'] ) && !in_array( $args['orderby'], $standard_array ) ) {
$args['meta_key'] = $args['orderby'];
$args['orderby'] = 'meta_value_num';
}
return $args;
}