像这样的方法会奏效：

<!--Child Page Thumbnails Start-->
<?php 
  $subs = new WP_Query( 
    array( 
      \'post_parent\' => $post->ID, 
      \'post_type\' => \'page\', 
      \'meta_key\' => \'_thumbnail_id\' 
    )
  );
if( $subs->have_posts() ) : 
  while( $subs->have_posts() ) : 
    $subs->the_post();
    echo \'<a href="\'.get_permalink().\'" title="\'.get_the_title().\'">\'.get_the_post_thumbnail().\'</a>\'.\'<br/><h2><a href="\'.get_permalink().\'">\'.get_the_title().\'</a></h2>\';
  the_content();    
  endwhile; 
endif; 
wp_reset_postdata(); ?>
<!--Child Page Thumbnails End-->