WooCommerce: add multiple products to cart via url

function webroom_add_multiple_products_to_cart( $url = false ) {
	// 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 $id_and_quantity ) {
		// Check for quantities defined in curie notation (<product_id>:<product_quantity>)
		
		$id_and_quantity = explode( ':', $id_and_quantity );
		$product_id = $id_and_quantity[0];

		$_REQUEST['quantity'] = ! empty( $id_and_quantity[1] ) ? absint( $id_and_quantity[1] ) : 1;

		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( $url );
		}

		$product_id        = apply_filters( 'woocommerce_add_to_cart_product_id', absint( $product_id ) );
		$was_added_to_cart = false;
		$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->get_type(), $adding_to_cart );

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

		// Grouped Products
		} elseif ( 'grouped' === $add_to_cart_handler ) {
			woo_hack_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 {
			woo_hack_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', 'webroom_add_multiple_products_to_cart', 15 );


/**
 * Invoke class private method
 *
 * @since   0.1.0
 *
 * @param   string $class_name
 * @param   string $methodName
 *
 * @return  mixed
 */
function woo_hack_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 );
	$args = array_merge( array( $reflection ), $args );
	return call_user_func_array( array( $method, 'invoke' ), $args );
}