How To Get WordPress Categories Link List?

I am trying to make a custom sitemap for my WordPress blogs categories. For that I added the below code in my functions.php file and when I save it, my Blog goes white. Nothing is showing up. I removed this code by going through FTP and then all got again fine.

Now I want to make and use this code. Now can anyone help me out to fix this code?

/* ------------------------------------------------------------------------- *
 *  Custom Dynamic XML Sitemap Generator For Categories
/* ------------------------------------------------------------------------- */
add_action("publish_post", "cat_create_sitemap");
add_action("publish_page", "cat_create_sitemap");
function cat_create_sitemap() {
  $categoriesForSitemap = get_categories(array(
    'hide_empty' => 0, 
    depth => 0, 
    'hierarchical' => false
  ));

  $sitemap = '<?xml version="1.0" encoding="UTF-8"?>';
  $sitemap .= '<?xml-stylesheet type="text/xsl" href="sitemap-style.xsl"?>';
  $sitemap .= '<urlset xmlns="http://ift.tt/xwbjRF">';

  foreach($categoriesForSitemap as $category) {
    setup_postdata($category);
    $categorydate = explode(" ", $category->category_modified);
    $sitemap .= '<url>'.
      '<loc>'. get_permalink($category->ID) .'</loc>'.
      '<priority>1</priority>'.
      '<lastmod>'. $categorydate[0] .'</lastmod>'.
      '<changefreq>daily</changefreq>'.
    '</url>';
  }
  $sitemap .= '</urlset>';
  $fp = fopen(ABSPATH . "custom-cat-sitemap.xml", 'w');
  fwrite($fp, $sitemap);
  fclose($fp);
}