Accept multiple product quantity add-to-cart in single request

add_action( 'template_redirect', function() {

	// Only For Multiple Add-to-cart Requests
	if(
		! class_exists( 'WC_Form_Handler' )
		|| empty( $_REQUEST['add-to-cart'] )
		|| ! strpos( $_REQUEST['add-to-cart'], ',' )
	) {
		return;
	}

	// Get Requests
	$product_ids = explode( ',', $_REQUEST['add-to-cart'] );
	$quantities = explode( ',', $_REQUEST['quantity'] );

	// Products And Quantity Counts Must Match
	if( count( $product_ids ) !== count( $quantities ) ) {
		return;
	}

	// Stop Default Handler
	remove_action( 'wp_loaded', [ 'WC_Form_Handler', 'add_to_cart_action' ], 20 );

	// Loop Add-to-cart Requests
	foreach( $product_ids as $i => $product_id ) {
		$product_id = absint( $product_id );
		$quantity = wc_stock_amount( absint( $quantities[$i] ) );
		$added_to_cart = WC()->cart->add_to_cart( $product_id, $quantity );
		if( $added_to_cart ) {
			wc_add_to_cart_message( [ $product_id => $quantity ], true );
		}
	}

} );