How do I exclude a specific page (and child pages) from the search results?

Question

How do I exclude a specific page (and child pages) from the search results?

I've seen posts showing how to exclude all pages. I don't want that. I want to target a page and it's children and exclude them and only them.

Answer 1

// Filter to exclude a page and it's child pages from search query
function myfilter_exclude_pages_from_search( $query ) {

    // Save the post id of the page to be excluded in $parent_post_id_to_exclude
    $parent_post_id_to_exclude = 111; // Replace 111 with actual page id
    // Convert the post id to an array
    $parent_post_id_arr = array( $parent_post_id_to_exclude ); 

    // Apply filter only if this is a search query and not on admin panel
    if ( $query->is_search && !is_admin() ) {

        // Search only for pages
        $query->set( 'post_type', 'page');

        // Exclude the page id
        $query->set( 'post__not_in', $parent_post_id_arr );

        // Exclude all child pages of selected page id
        $query->set( 'post_parent__not_in', $parent_post_id_arr );
    }
    return $query;
}
add_filter( 'pre_get_posts', 'myfilter_exclude_pages_from_search' );

Read below article for other use cases for pre_get_posts
https://www.wpbeginner.com/plugins/how-to-exclude-specific-pages-authors-and-more-from-wordpress-search/

Reference for parameters to WP_Query : https://developer.wordpress.org/reference/classes/wp_query/