function woocommerce_maybe_add_multiple_products_to_cart() {
    // Make sure WC is installed, and add-to-cart qauery arg exists, and contains at least one comma.
    if ( ! class_exists( 'WC_Form_Handler' ) || empty( $_REQUEST['add-to-cart'] ) || false === strpos( $_REQUEST['add-to-cart'], ',' ) ) {
        return;
    }

    // Remove WooCommerce's hook, as it's useless (doesn't handle multiple products).
    remove_action( 'wp_loaded', array( 'WC_Form_Handler', 'add_to_cart_action' ), 20 );

    $product_ids = explode( ',', $_REQUEST['add-to-cart'] );
    $count       = count( $product_ids );
    $number      = 0;

    foreach ( $product_ids as $product_id ) {
        if ( ++$number === $count ) {
            // Ok, final item, let's send it back to woocommerce's add_to_cart_action method for handling.
            $_REQUEST['add-to-cart'] = $product_id;

            return WC_Form_Handler::add_to_cart_action();
        }

        $product_id     = apply_filters( 'woocommerce_add_to_cart_product_id', absint( $product_id ) );
        $adding_to_cart = wc_get_product( $product_id );

        if ( ! $adding_to_cart ) {
            continue;
        }

        $add_to_cart_handler = apply_filters( 'woocommerce_add_to_cart_handler', $adding_to_cart->product_type, $adding_to_cart );

        // Variable product handling
        if ( 'variable' === $add_to_cart_handler ) {
            jt_invoke_private_method( 'WC_Form_Handler', 'add_to_cart_handler_variable', $product_id );

        // Grouped Products
        } elseif ( 'grouped' === $add_to_cart_handler ) {
            jt_invoke_private_method( 'WC_Form_Handler', 'add_to_cart_handler_grouped', $product_id );

        // Custom Handler
        } elseif ( has_action( 'woocommerce_add_to_cart_handler_' . $add_to_cart_handler ) ){
            do_action( 'woocommerce_add_to_cart_handler_' . $add_to_cart_handler, $url );

        // Simple Products
        } else {
            jt_invoke_private_method( 'WC_Form_Handler', 'add_to_cart_handler_simple', $product_id );
        }
    }
}

// Fire before the WC_Form_Handler::add_to_cart_action callback.
add_action( 'wp_loaded', 'woocommerce_maybe_add_multiple_products_to_cart', 15 );


/**
 * Makes private static methods available. All parameters after the first two ($class_name, $methodname)
 * will be passed into the method.
 *
 * @param  string  $class_name The class name.
 * @param  string  $methodName The method name.
 *
 * @return mixed               The result of the method call.
 */
function jt_invoke_private_method( $class_name, $methodName ) {
    if ( version_compare( phpversion(), '5.3', '<' ) ) {
        throw new Exception( 'PHP version does not support ReflectionClass::setAccessible()', __LINE__ );
    }

    $args = func_get_args();
    unset( $args[0], $args[1] );
    $reflection = new ReflectionClass( $class_name );
    $method = $reflection->getMethod( $methodName );
    $method->setAccessible( true );

    $args = array_merge( array( $class_name ), $args );
    return call_user_func_array( array( $method, 'invoke' ), $args );
}