如果有人与这样的问题发生冲突，我会这样解决：

$attachments = get_posts( array(
    \'post_type\'      => \'attachment\',
    \'posts_per_page\' => -1,
    \'post_status\'    => \'any\',
    \'post_parent\'    => $post_id
) );
$thumbId = get_post_thumbnail_id($post_id);
foreach ( $attachments as $attachment ) {
    if($thumbId != $attachment->ID) wp_delete_attachment( $attachment->ID, true );
}