Excludes protected posts from WP search results

maybe-exclude-protected-posts.php

<?php

function maybe_exclude_protected_posts($query) {
  if(!$query->is_admin && $query->is_search && $query->is_main_query()) {
    $posts_to_exclude = array();
    $posts = get_posts(array('numberposts' => -1));

    foreach($posts as $post) {
      if(MeprRule::is_locked($post)) {
        $posts_to_exclude[] = $post->ID;
      }
    }

    if(!empty($posts_to_exclude)) {
      $query->set('post__not_in', $posts_to_exclude);
    }
  }
}
add_action('pre_get_posts', 'maybe_exclude_protected_posts');