SiteMapServices.php

<?php
namespace App\Services;
use App\Post;
use Carbon\Carbon;
use Illuminate\Support\Facades\Cache;
class SiteMap
{
  /**
   * Return the content of the Site Map
   */
  public function getSiteMap()
  {
    if (Cache::has('site-map')) {
      return Cache::get('site-map');
    }
    $siteMap = $this->buildSiteMap();
    Cache::add('site-map', $siteMap, 120);
    return $siteMap;
  }
  /**
   * Build the Site Map
   */
  protected function buildSiteMap()
  {
    $postsInfo = $this->getPostsInfo();
    $dates = array_values($postsInfo);
    sort($dates);
    $lastmod = last($dates);
    $url = trim(url(), '/') . '/';
    $xml = [];
    $xml[] = '<?xml version="1.0" encoding="UTF-8"?'.'>';
    $xml[] = '<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">';
    $xml[] = '  <url>';
    $xml[] = "    <loc>$url</loc>";
    $xml[] = "    <lastmod>$lastmod</lastmod>";
    $xml[] = '    <changefreq>daily</changefreq>';
    $xml[] = '    <priority>0.8</priority>';
    $xml[] = '  </url>';
    foreach ($postsInfo as $slug => $lastmod) {
      $xml[] = '  <url>';
      $xml[] = "    <loc>{$url}blog/$slug</loc>";
      $xml[] = "    <lastmod>$lastmod</lastmod>";
      $xml[] = "  </url>";
    }
    $xml[] = '</urlset>';
    return join("\n", $xml);
  }
  /**
   * Return all the posts as $url => $date
   */
  protected function getPostsInfo()
  {
    return Post::where('published_at', '<=', Carbon::now())
      ->where('is_draft', 0)
      ->orderBy('published_at', 'desc')
      ->lists('updated_at', 'slug')
      ->all();
  }
}