function woocommerce_template_loop_add_to_cart()
 {
     global $product;
     if ($product->product_type == "simple") {
         woocommerce_simple_add_to_cart();
     } else {
         woocommerce_get_template('loop/add-to-cart.php');
     }
 }
 public function simple_add_to_cart()
 {
     global $woocommerce, $product;
     ob_start();
     woocommerce_simple_add_to_cart();
     $button = ob_get_clean();
     /*modify button class so that AJAX add-to-cart script finds it*/
     $replacement = sprintf('data-product_id="%d" data-quantity="1" $1 add_to_cart_button product_type_simple ', $product->id);
     $button = preg_replace('/(class="single_add_to_cart_button)/', $replacement, $button);
     echo $button;
 }
/**
* customise Add to Cart link/button for product loop
* @param string $button
* @param object $product
* @return string
*/
function custom_woo_loop_add_to_cart_link($button, $product)
{
    // not for variable, grouped or external products
    if (!in_array($product->product_type, array('variable', 'grouped', 'external'))) {
        // only if can be purchased
        if ($product->is_purchasable()) {
            // show qty +/- with button
            ob_start();
            woocommerce_simple_add_to_cart();
            $button = ob_get_clean();
            // modify button so that AJAX add-to-cart script finds it
            $replacement = sprintf('data-product_id="%d" data-quantity="1" $1 add_to_cart_button product_type_simple ', $product->id);
            $button = preg_replace('/(class="single_add_to_cart_button)/', $replacement, $button);
        }
    }
    return $button;
}
{
    $orderby_value = isset($_GET['orderby']) ? woocommerce_clean($_GET['orderby']) : apply_filters('woocommerce_default_catalog_orderby', get_option('woocommerce_default_catalog_orderby'));
    if ('sku' == $orderby_value) {
        $args['orderby'] = 'meta_value';
        $args['order'] = 'asc';
        $args['meta_key'] = '_sku';
    }
    return $args;
}
add_filter('woocommerce_default_catalog_orderby_options', 'custom_woocommerce_catalog_orderby');
add_filter('woocommerce_catalog_orderby', 'custom_woocommerce_catalog_orderby');
function custom_woocommerce_catalog_orderby($sortby)
{
    $sortby['sku'] = 'Sort by sku';
    return $sortby;
}
//remove price
remove_action('woocommerce_after_shop_loop_item_title', 'woocommerce_template_loop_price', 10);
remove_action('woocommerce_single_product_summary', 'woocommerce_template_single_price', 10);
remove_action('woocommerce_single_product_lightbox_summary', 'woocommerce_template_single_price', 10);
//remove add to cart
remove_action('woocommerce_single_product_summary', 'woocommerce_template_single_add_to_cart', 30);
remove_action('woocommerce_simple_add_to_cart', 'woocommerce_simple_add_to_cart', 30);
remove_action('woocommerce_grouped_add_to_cart', 'woocommerce_grouped_add_to_cart', 30);
remove_action('woocommerce_variable_add_to_cart', 'woocommerce_variable_add_to_cart', 30);
remove_action('woocommerce_external_add_to_cart', 'woocommerce_external_add_to_cart', 30);
remove_action('woocommerce_single_product_lightbox_summary', 'woocommerce_template_single_add_to_cart', 30);
$order->add_order_note(sprintf("Shipping label available at: '%s'", $shipment->postage_label->label_url));
//get add to cart form
woocommerce_simple_add_to_cart();
 function add_to_cart()
 {
     woocommerce_simple_add_to_cart();
 }