$query = new Posts();
if (count(Auth::user()->tags) > 0) {
   $query = $query->whereHas('tags', function ($q) {
        $i = 0;
        foreach (Auth::user()->tags as $tag) {
            if ($i == 0) {
                $q->where('title', '=', $tag->title);
            } else {
                $q->orWhere('title', '=', $tag->title);
            }
            $i++;
        }
    });
}
$posts = $query->where('isTemplate', true)->orderBy($key, $order)->paginate(15);

$query = Posts::query()
              ->where('isTemplate', true)
              ->orderBy($key, $order);
if (Auth::user()->tags->isNotEmpty()) {
  $tags = Auth::user()
                ->tags
                ->pluck('title')
                ->toArray();
  $query = $query->whereIn('tags', $tags);
}
$posts = $query->paginate(15);