How to Generate sitemap.xml file when new post added into WordPress website

Automatically Generate sitemap.xml file when new post added into WordPress website

1. Login into WordPress admin
2. Choose Appearance
3. Choose theme editor
4. Select your theme
5. Open functions.php file into editor
6. Add below code at the end of file

/**
 * start page for webaccess
 * redirect the user to the supported page type by the users webbrowser (js available or not)
 *
 * PHP version 5
 *
 * @category  PHP
 * @package   aditya
 * @author   Aditya Kumar <adityaypi@yahoo.com>
 * @link      http://adityakumarsingh.co.in
************************************
*HTML Sitemap   in WordPress   
************************************/

function sitemap() {
    $sitemap = '';
    $sitemap .= '<h4>Articles </h4>';
    $sitemap .= '<ul class="sitemapul">';
    $posts_array = get_posts();
    foreach ($posts_array as $spost):
        $sitemap .='<div class="blockArticle">
            <h3><a href="' . $spost->guid . '" rel="bookmark" class="linktag">' . $spost->post_title . '</a> </h3>
        </div>';
    endforeach;
    $sitemap .= '</ul>';
    $sitemap .= '<h4>Category</h4>';
    $sitemap .= '<ul class="sitemapul">';
    $args = array(
        'offset' => 0,
        'category' => '',
        'category_name' => '',
        'orderby' => 'date',
        'order' => 'DESC',
        'include' => '',
        'exclude' => '',
        'meta_key' => '',
        'meta_value' => '',
        'post_type' => 'post',
        'post_mime_type' => '',
        'post_parent' => '',
        'author' => '',
        'post_status' => 'publish',
        'suppress_filters' => true
    );
    $cats = get_categories($args);
    foreach ($cats as $cat) :
        $sitemap .= '<li class="pages-list"><a href="' . get_category_link($cat->term_id) . '">' . $cat->cat_name . '</a></li>';
    endforeach;
    $sitemap .= '</ul>';
    $pages_args = array(
        'exclude' => '', /* ID of pages to be excluded, separated by comma */
        'post_type' => 'page',
        'post_status' => 'publish'
    );
    $sitemap .= '<h3>Pages</h3>';
    $sitemap .= '<ul>';
    $pages = get_pages($pages_args);
    foreach ($pages as $page) :
        $sitemap .= '<li class="pages-list"><a href="' . get_page_link($page->ID) . '" rel="bookmark">' . $page->post_title . '</a></li>';
    endforeach;
    $sitemap .= '</ul>';
    $sitemap .= '<h4>Tags</h4>';
    $sitemap .= '<ul class="sitemapul">';
    $tags = get_tags();
    foreach ($tags as $tag) {
        $tag_link = get_tag_link($tag->term_id);
        $sitemap .= "<li class='pages-list'><a href='{$tag_link}' title='{$tag->name} Tag' class='{$tag->slug}'>";
        $sitemap .= $tag->name . '</a></li>';
    }
    return$sitemap;
}
add_shortcode('sitemap', 'sitemap');


/****************************************************
* XML Sitemap in WordPress
*****************************************************/

function xml_sitemap() {
  $postsForSitemap = get_posts(array(
    'numberposts' => -1,
    'orderby' => 'modified',
    'post_type'  => array('post','page'),
    'order'    => 'DESC'
  ));

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

  foreach($postsForSitemap as $post) {
    setup_postdata($post);

    $postdate = explode(" ", $post->post_modified);

    $sitemap .= '<url>'.
      '<loc>'. get_permalink($post->ID) .'</loc>'.
      '<lastmod>'. $postdate[0] .'</lastmod>'.
      '<changefreq>monthly</changefreq>'.
    '</url>';
  }

  $sitemap .= '</urlset>';

  $fp = fopen(ABSPATH . "sitemap.xml", 'w');
  fwrite($fp, $sitemap);
  fclose($fp);
}

add_action("publish_post", "xml_sitemap");
add_action("publish_page", "xml_sitemap");