Generate an array of parent/child page IDs, based on parent page name

OK, so what we want to achieve is to write a function that will take a title of a page and return the array containing its ID and IDs of its children. So here’s the code:

function get_page_and_its_children_ids_by_title( $page_title ) {
    $result = array();

    $page = get_page_by_title( $page_title );  // find page with given title
    if ( $page ) {  // if that page exists
        $result[] = $page->ID;  // add its ID to the result
        $children = get_children( array(  // get its children 
            'post_parent' => $page->ID,
            'post_type'   => 'page', 
            'numberposts' => -1,
            'post_status' => 'publish' 
        ) );
        $result = array_merge( $result, array_keys( $children ) );  // add children ids to the result
    }

    return $result;
}