您可以使用get_ancestors() 检查帖子是否有祖父母id或祖父母id等。。

但是你必须检查每一个帖子。。。

function rt_before_after($content) {
    if(is_page() || is_single()) {
      global $post;
      $ancestors = get_ancestors( $post->ID, \'page\' );
      if ( in_array( 27, $ancestors ) || $post->ID == \'27\') {
        $ntest=\'<div class="clearlogo"><img alt="nodal Clear logo" width="150" src="\'.get_stylesheet_directory_uri().\'/images/nodal-clear-logo.png"></div>\';
      }else{
        $ntest=\'\';
      }
        $beforecontent = $ntest.\'<h1 class="title">\'.get_the_title().\'</h1>\';

        $fullcontent = $beforecontent . $content;
    } else {
        $fullcontent = $content;
    }

    return $fullcontent;
}
add_filter(\'the_content\', \'rt_before_after\');

使用这种方法，您可以将其移动到单独的函数并调用一次，如果需要，甚至可以缓存它。我会选择第二种方法。

function rt_before_after($content) {
    if(is_page() || is_single()) {
      global $post;

      // get all the child pages and grandchild etc..
      $pages = get_pages( [\'child_of\'=>27] );
      $pages_ids = array_map( function( $item ) {
        return $item->ID;
      }, $pages );

      if ( in_array( $post->ID, $pages_ids ) || $post->ID == \'27\') {
        $ntest=\'<div class="clearlogo"><img alt="nodal Clear logo" width="150" src="\'.get_stylesheet_directory_uri().\'/images/nodal-clear-logo.png"></div>\';
      }else{
        $ntest=\'\';
      }
        $beforecontent = $ntest.\'<h1 class="title">\'.get_the_title().\'</h1>\';

        $fullcontent = $beforecontent . $content;
    } else {
        $fullcontent = $content;
    }

    return $fullcontent;
}
add_filter(\'the_content\', \'rt_before_after\');