function generate_sitemap() {
    // Get the base URL of the site
    $site_url = home_url('/');
    
     $posts = get_posts(array(
        'numberposts' => -1,
        'post_type'   => array('post', 'page'),
        'post_status' => 'publish',
        'orderby'     => 'post_date',
        'order'       => 'DESC',
        'suppress_filters' => true 
    ));

    // Start building the XML structure
    $sitemap = '<?xml version="1.0" encoding="UTF-8"?>';
    $sitemap .= '<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">';

    // Add homepage entry
    $sitemap .= '<url>';
    $sitemap .= '<loc>' . esc_url($site_url) . '</loc>';
    $sitemap .= '<lastmod>' . date('Y-m-d') . '</lastmod>';
    $sitemap .= '<changefreq>weekly</changefreq>';
    $sitemap .= '<priority>1.0</priority>';
    $sitemap .= '</url>';


    $url_list = array();

    // Loop through all posts and pages
    foreach ($posts as $post) {
        $post_url = get_permalink($post->ID);
        $last_modified = get_the_modified_date('Y-m-d', $post->ID);


        if (!in_array($post_url, $url_list)) {
            $sitemap .= '<url>';
            $sitemap .= '<loc>' . esc_url($post_url) . '</loc>';
            $sitemap .= '<lastmod>' . $last_modified . '</lastmod>';
            $sitemap .= '<changefreq>monthly</changefreq>';
            $sitemap .= '<priority>0.8</priority>';
            $sitemap .= '</url>';

            // Add the URL to the array to track duplicates
            $url_list[] = $post_url;
        }
    }


    $sitemap .= '</urlset>';

    // Write the sitemap file to the root directory (sitemap.xml)
    $file = ABSPATH . 'sitemap.xml';
    file_put_contents($file, $sitemap);
}

add_action('init', 'generate_sitemap');