Hi Nino, I removed your code examples from your reply as it became a mess in the backoffice. Please use pastebin or github gists to show your code. For combining multiple filters at once, I will add an additional section in my blog post. You need to build up your $args before you make the new WP_Query. Here’s a small example of how you can build your args query. I will try to expand my post over the weekend but hopefully this snippet can get you started.

// Set your default query params
$args = [
   'post_type'      => 'product',
   'posts_per_page' => -1,
   'post_status'    => 'publish',
   'orderby'        => 'date',
   'order'          => 'desc',
];

// Add each extra taxonomy query like this:
$args['tax_query'][] = [
   'taxonomy'      => 'product_cat',
   'field'	   => 'term_id',
   'terms'         => $catIds,
   'operator'      => 'IN'
];

// Make a new WP_Query with the $args array
$ajaxproducts = new WP_Query($args);

Thank you very much Bob for the fast reply. I will try to explain myself. I have figured it out I able to sort based on taxonomy. I would like to use 2 SELECT for 2 different taxonomies one for themes and one for subjects which are 2 taxonomies. How can I use a SELECT for multiple tax filtering? When is select one dropdown option it will filter all over again, is there a way I can simply do this? So basically giving users the option to filter on 2 select fields instead of one.

Hi Nino, I removed a bit from your code as it became too long. I left the query part in your answer. If you’re not using categories, you need to remove the ‘category_name’ from the arguments. The Tax Query in my previous example was filled with dummy content. You need to change the custom-taxonomy and your-term-slug with your actual taxonomy.

Hi Bob,

How can I add code here? For some reason, It is just not working for me.

Hey Bob,

I have created a custom taxonomy themes with multiple values in the back-end. I am able to return them when looping through them. But filtering is not working. I am not using categories but would like to filter by taxonomy. I have tried to apply your code but without luck.

function filter_updates() {
    $postType = $_POST['type'];
    $catSlug = $_POST['category'];

  $ajaxposts = new WP_Query([
    'post_type' => $postType,
    'posts_per_page' => -1,
    'category_name' => $catSlug,
    'orderby' => 'menu_order',
    'order' => 'desc',
    'tax_query' => [
        [
           'taxonomy' => 'custom-taxonomy',
           'field'    => 'slug',
           'terms'    => array('your-term-slug'),
        ],
     ]
  ]);
}

Could you see what is causing this issue? When trying to filter it returns only one post.

Hi Nino,
For custom taxonomies you need to change your query to something like this:

$projects = new WP_Query([
   'post_type' => 'projecten',
   'posts_per_page' => -1,
   'tax_query' => [
      [
         'taxonomy' => 'custom-taxonomy',
         'field'    => 'slug',
         'terms'    => array('your-term-slug'),
         'operator' => 'IN'
      ],
   ]
]);

It's untested so let me know if it works correctly for taxonomies. I'll add it to the article if it does.

What do I have to change to filter on a taxonomy instead of a category? What do I have to change?

Thanks!