public function index()
 {
     $articles = Article::select(['id', 'title', 'user_id', 'category_id', 'updated_at', 'created_at', 'deleted_at'])->paginate(10);
     foreach ($articles as $v) {
         $v->last_reply = $v->comment->max('created_at');
     }
     return view('admin.article.index')->with('articles', $articles);
 }
 public static function hotTag()
 {
     $tag = Article::select(['id', 'tag'])->whereNull('deleted_at')->orderBy('view', 'desc')->take(10)->get();
     $data = array();
     foreach ($tag as $v) {
         $data = array_merge($data, explode(',', $v->tag));
     }
     $data = array_unique($data);
     return $data;
 }