Taxonomy slugs

function my_dropdown($name, $taxonomy = 'category')
    {
        $defaults = array(
            'taxonomy' => $taxonomy,
            'id'       => $name,
            'name'     => $name,
            'show_option_none' => ' - Select - ',
            'selected' => get_query_var($name)
    );
    wp_dropdown_categories($defaults);
    }
    add_action('pre_get_posts', 'my_customsearch');
    
    
    function my_customsearch()
    {
    global $wp_query;


    if ( $wp_query->query_vars['post_type'] != 'schedahotel' ||
         !$wp_query->is_post_type_archive ) {
        return false;
    }
        
    $tax_query = array();
    $topic = get_query_var('topic');
    $title = get_query_var('title');


    // first dropdown
    if (!empty($topic) && $topic > 0) {
        $tax_query[] = array(
            'taxonomy' => 'topic',
            'field'    => 'slug',
            'terms'    => $topic
        );
    } 


    // second dropdown
    if (!empty($title) && $title > 0) {
        $tax_query[] = array(
            'taxonomy' => 'title',
            'field'    => 'slug',
            'terms'    => $title
        );
    }




    if ( sizeof($tax_query) > 0 ) {
        $tax_query['relation'] = 'AND';
        $wp_query->query_vars['tax_query'] = $tax_query;
    }


    


    return false;


}






// }}}


// {{{






// add my custom query vars
add_filter('query_vars', 'mycustom_query_vars');






function mycustom_query_vars($query_vars)
{
    $query_vars[] = 'topic';
    $query_vars[] = 'title';
    return $query_vars;
}