WORDPRESS: TAGS IN A CATEGORY

gistfile1

    query_posts('category_name=category-slug');
    if (have_posts()) :
      while (have_posts()) : the_post();
        $posttags = get_the_tags();
        if ($posttags) {
          foreach($posttags as $tag) {

            $all_tags_arr[] = $tag->name; //USING JUST $tag MAKING $all_tags_arr A MULTI-DIMENSIONAL ARRAY, WHICH DOES WORK WITH array_unique

          }
        }
      endwhile;
    endif;
    $tags_arr = array_unique($all_tags_arr); //REMOVES DUPLICATES

    foreach ($tags_arr as $tag) {
          # code...
          echo $tag;
    }