I have a custom post type, and have created an archive template, archive-custom_post_type.php, which includes a search form.

I am then using pre_get_posts to add parameters to the query to filter my results.

However, to make sure this only happens on this archive page, I want to check a few things. First I am checking if the post type matches.

But then I wanted to check the is_search() parameter, only to see that it is false.

How and when is this defined? Can I do anything to let WP know that a search is happening?

pre_get_posts callback

$post_type = get_query_var( 'post_type' );

if ( $post_type === 'document' ) {
    $params = $_POST;

    if ( $params ) {
        $query->set( 's', $params['keyword'] );
        $query->set( 'order', $params['order'] );
        $query->set( 'orderby', $params['order_by'] );


<?php get_header(); ?>

<?php get_template_part( 'my-slug', 'document-filter' ); ?>

<div id="search-results">

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>

        <?php the_title(); ?>

<?php endwhile; else : ?>
    <p>Sorry, no posts matched your criteria</p>
<?php endif; ?>


<?php get_footer(); ?>


<form id="document-filter" method="post">
    <select name="order_by">
        <option value="date">Date</option>
        <option value="title">Name</option>
    <select name="order">
        <option value="desc">DESC</option>
        <option value="asc">ASC</option>
    <input name="keyword" type="text" placeholder="Filter by keyword" value=""/>
    <input type="submit" />
  • Can you show us some code?
    – Z. Zlatev
    Aug 30, 2017 at 11:46

1 Answer 1


Name your keyword input just s

<input name="s" type="text" placeholder="Filter by keyword" value=""/>

This is enough for WP to recognize the request as search plus you won't have to do the $query->set( 's', ... ) later

In pre_get_posts action use the conditional is_post_type_archive( 'document' ) so your if statement look something like this:

if ( is_post_type_archive('document') && is_search() ) {

Hope that helps


Since you're searching, search template (search.php, index.php) will take precedence over the archive. You will need to filter the template which WP assigns for those requests as well.

add_filter( 'search_template', function ( $template ) {
  if ( is_post_type_archive('document') && is_search() ) {
    $find_template = locate_template( ['archive-document.php'] );

    if ( '' !== $find_template ) {
      $template = $find_template;

  return $template;
  • that does seem to work, but now my results are displayed on the default search results page, instead of my archive page, and there for the styling is different and more importantly, by custom search form is not shown. This search is ONLY for this archive, so is there a way to has a custom archive search result page, to show my custom search form and my custom styling?
    – Mr Pablo
    Aug 30, 2017 at 13:19
  • Hmm, looks like I can use get_template_part() in the search result page to load the archive page again. How do I go about using pagination though now?
    – Mr Pablo
    Aug 30, 2017 at 13:28
  • That's expected. See my updated answer
    – Z. Zlatev
    Aug 30, 2017 at 13:30

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