Query taxonomies depending on specific category - Wordpress

Question

I'm trying to configure a filter navigation where the filters fetched are chosen by the taxonomy 'underkategorier' (Sub categories in Swedish).

The problem I'm having is that I have two pages of which both query different kinds of categories. But for some reason I can't get my list of custom taxonomy links to just list objects within that specific category. One page lists custom posts from Category nr 9 and the other lists custom posts from category 10.

My query is as follows,

<?php $queryname = array(
'post_type'      => 'projekt',
'cat'     => 9,
'order'    => 'ASC',
'posts_per_page' => '-1',); query_posts( $queryname ); ?>

And my taxonomy list of links is as follows,

     <?php $terms = get_terms('underkategorier'); $count = count($terms);  if ( $count > 0 ){
 echo "<div class='post-tags'><a data-filter='all' class='tax-filter filter'>Visa alla</a>";
 foreach ( $terms as $term ) {
   echo "<a data-filter='.$term->slug' class='tax-filter filter'>" . $term->name . '&nbsp;(' . $term->count . ")</a>";      
 }
 echo "</div>";} ?>

So. I want to display links of category 9 + taxonomy 'underkategorier'. Not posts, but terms. For example if 'underkategorier' has a few terms like, 'buildings', 'parks', railways' I want do display these as links. But only if they belong to category 9 as well. So if there where a fourth 'underkategori' by name 'stadiums' which belonged to a category 10 post, this would not show up on the page that displays category 9 posts.

I am still quite new to these coding parts and I could really use some help and would be very grateful. If my question is fuzzy please let me know and I'll try to rephrase. When I get it right I will share it with you all for future help.

Answer 1

This will find all terms in custom taxonomy 'underkategorier' and then will show terms with post from chosen category.

$taxonomies = get_taxonomies(array('name'=>'underkategorier'),'object'); 
foreach($taxonomies as $taxonomy){
    $terms = get_terms( $taxonomy->name, 'orderby=count&hide_empty=0' );
    foreach($terms as $term){
        $wpq = array ('taxonomy'=>'underkategorier','term'=>$term->slug, "cat"=>10);
        $myquery = new WP_Query ($wpq);
        $article_count = $myquery->post_count; 
        echo $term->name.' '.$article_count; //with empty ones
        if ($article_count){
        echo "<ul>";
        echo "<li>".$term->name.' '.$article_count."</li>";
        echo "</ul>";
        }
    }
}