<h2>Final test</h2>

<?php
$cat_id = $category->cat_ID;
global $post;
$category_posts = new WP_Query('cat=cat_id');
$all_tags = array();
while ( $category_posts->have_posts() ) : $category_posts->the_post();
	$tags = wp_get_post_terms(get_the_ID(), 'post_tag');


	foreach($tags as $tag)
		$all_tags[$tag->term_id][] = get_the_ID();
		var_dump($tags);
endwhile;

foreach($all_tags as $key => $tag) {
	$term_id = get_term($key);
	$term = get_term($term_id, 'post_tag');
	echo $term->name . '<BR>';
	foreach($tag as $post_id) {
		echo '<a href="' . get_permalink($post_id) . get_the_title($post_id) . "></a><BR>";
	}

}

?>