tag cloud made from specific category

I found this, is this proper?

https://www.wprecipes.com/get-tags-specific-to-a-particular-category-on-your-wordpress-blog

<?php
	query_posts('category_name=html');
	if (have_posts()) : while (have_posts()) : the_post();
        $posttags = get_the_tags();
		if ($posttags) {
			foreach($posttags as $tag) {
				$all_tags_arr[] = $tag -> name;
			}
		}
	endwhile; endif; 

	$tags_arr = array_unique($all_tags_arr);
?>
	<ul>
<?php
	foreach($tags_arr as $tag){
		echo '<li>'.$tag.'</li>';
	}
?>
</ul>
<?php wp_reset_query(); ?>

Here is updated code for when someone along the way comes to a similar question. This example uses a better core wordpress function to simplify the process. Just change the category name. If there is a simpler way, feel free to chime in.

<?php query_posts('category_name=html');
                if (have_posts()) : while (have_posts()) : the_post();

                    if( get_the_tag_list() ){
                        $posttags = get_the_tag_list('<ul><li>','</li><li>','</li></ul>');
                    }

                endwhile; endif;
                echo $posttags;

                wp_reset_query();
?>

If you haven’t got a solution to this problem, this solution works: https://www.webtechwise.com/creating-tag-list-or-tag-cloud-for-a-specific-category/