WordPress search form & results for custom post type

search.php

<?php

// store the post type from the URL string
$post_type = $_GET['post_type'];

// check to see if there was a post type in the
// URL string and if a results template for that
// post type actually exists
if ( isset( $post_type ) && locate_template( 'search-' . $post_type . '.php' ) ) {

  // if so, load that template
  get_template_part( 'search', $post_type );
  
  // and then exit out
  exit;
}

?>

<!-- default search results here -->

searchform-kb_article.php

<form class="search" action="<?php echo home_url( '/' ); ?>">
  <input type="search" name="s" placeholder="Search&hellip;">
  <input type="submit" value="Search">
  <input type="hidden" name="post_type" value="kb_article">
</form>