woocommerce create image gallery for products

I have create a woocommerce product update and i upload an image as product image with the follow php code. Now i want also to create and a product gallery.
Any idea for that?

function Generate_Featured_Image( $image_url, $product_id, $product_title  )
{
    $upload_dir = wp_upload_dir();
    $image_data = file_get_contents($image_url);        


    $product = new WC_product($product_id);
    $tmp_image_id = $product->get_image_id();

    if ($tmp_image_id > 0 )
        wp_delete_attachment($tmp_image_id);

    if ($image_data === FALSE)
        return false;


    $filename = basename($image_url);
    if(wp_mkdir_p($upload_dir['path']))     $file = $upload_dir['path'] . '/' . $filename;
    else                                    $file = $upload_dir['basedir'] . '/' . $filename;
    file_put_contents($file, $image_data);

    $wp_filetype = wp_check_filetype($filename, null );
    $attachment = array(
        'post_mime_type' => $wp_filetype['type'],
        'post_title' => $product_title,
        'post_content' => '',
        'post_status' => 'inherit'
    );
    $attach_id = wp_insert_attachment( $attachment, $file, $product_id );
    require_once(ABSPATH . 'wp-admin/includes/image.php');
    $attach_data = wp_generate_attachment_metadata( $attach_id, $file );
    $res1= wp_update_attachment_metadata( $attach_id, $attach_data );
    $res2= set_post_thumbnail( $product_id, $attach_id );
}