php tools/spark install codeigniter-sitemaps

//if you're using sparks
$this->load->spark('codeigniter-sitemaps/0.0.1')

$this->load->library('sitemaps');

//assuming a hypothetical posts_model
$posts = $this->posts_model->get_posts();

    foreach ($posts AS $post)
    {
        $item = array(
            "loc" => site_url("blog/" . $post->slug),
            "lastmod" => date("c", strtotime($post->last_modified)),
            "changefreq" => "hourly",
            "priority" => "0.8"
        );

        $this->sitemaps->add_item($item);
    }

// file name may change due to compression
$file_name = $this->sitemaps->build("sitemap_blog.xml");

$reponses = $this->sitemaps->ping(site_url($file_name));