I am trying to query a custom post type based on what a user inputs into a form, I am having trouble querying multiple taxonomies in pre_get_posts filter, I can't seem to find a way to set the query more than one taxonomy

function custom_search( $query ) {
if ( is_archive('experts') && $query->is_main_query() && !is_admin() ) {

    $keyword = get_query_var( 'keyword', FALSE );
    $industry_select = strtolower(str_replace(' ', '-', get_query_var( 'industry_select', FALSE ) ));
    $speciality_select = strtolower(str_replace(' ', '-', get_query_var( 'speciality', FALSE ) ));
    // Keywords query
    $keyword ? $keyword : $keyword = null;

    $query->set('s', $keyword);
    // Taxonomies query

    $tax_query_array = array('relation' => 'OR');
    $speciality_select ? array_push($tax_query_array, array('taxonomy' => 'experts_specialities', 'field' => 'slug', 'terms' => $speciality_select) ) : null ;
    $query->set( 'tax_query', $tax_query_array);

    $tax_query_array = array('relation' => 'OR');
    $industry_select ? array_push($tax_query_array, array('taxonomy' => 'experts_industries', 'field' => 'slug', 'terms' => $industry_select) ) : null ;
    $query->set( 'tax_query', $tax_query_array);
add_action( 'pre_get_posts', 'custom_search' );

In the past I have written queries that look like the following that successfully look in two taxonomies (eventually I need to have 3 taxonomies though)

$featured_args = array(
    'post_type'  => 'experts',
    'hide_empty' => false ,
    'paged'      => $paged,
    'tax_query' => array(
            'taxonomy' => 'experts_industries',
            'field' => 'slug',
            'terms' => $broad_match_ind
            'taxonomy' => 'experts_specialities',
            'field' => 'slug',
            'terms' => $broad_match_spec

I'm trying to use pre_get_posts because I ultimately want the results of this query on an archive page and don't want to create a second query with a set of args ( as I am currently doing as evidenced by my second code example above )

Thanks in advance.

  • The 2nd $tax_query_array = array('relation' => 'OR'); overrides the previous array.. Also, is_archive() does not accept any parameters - use is_post_type_archive() to check for a specific post type archive.
    – Sally CJ
    Apr 6, 2022 at 23:11
  • Ah yeah I see that now, thanks for the pointing that out. Probably staring at it too long.. So something the following should work? $tax_query_array = array('relation' => 'OR'); $industry_select ? array_push($tax_query_array, $tax_query_args ) : null ; $query->set( 'tax_query', $tax_query_array); }} ( I don't have a chance to try it out at the moment or I would just do that ), just asking for reference when I try tomorrow morning. Thanks. Apr 7, 2022 at 3:43
  • See my answer :)
    – Sally CJ
    Apr 7, 2022 at 10:11

1 Answer 1


I can't seem to find a way to set the query more than one taxonomy

You already found it, but the problem is, you should have not done this:

$tax_query_array = array('relation' => 'OR');
$speciality_select ? array_push($tax_query_array, ...) : null ;
$query->set( 'tax_query', $tax_query_array);

$tax_query_array = array('relation' => 'OR');
$industry_select ? array_push($tax_query_array, ...) : null ;
$query->set( 'tax_query', $tax_query_array);

.. because the 2nd $query->set() call overrides the entire tax_query array that's set via the 1st $query->set() call.

And to fix the issue, just remove the 1st $query->set() call and the 2nd $tax_query_array = array('relation' => 'OR');, i.e. lines 3 and 5 above.

Also, keep in mind that is_archive() does not accept any parameters. So if you wanted to check if the query is for a specific post type archive, use is_post_type_archive() instead, i.e. is_post_type_archive( 'experts' ).

And.. I don't think the $keyword ? $keyword : $keyword = null; is necessary, so I'd just remove that and simply do $query->set('s', $keyword);.

  • 1
    That'll do it! Thank you. I appreciate the help! Apr 7, 2022 at 14:51

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