以下是我的功能：

function insert_img_rel_attrib( $html, $id, $caption, $title, $align, $url  )
{
  $postID = ???
  $rel = "<a rel=\'shadowbox[".$postID."]\'";
  if ($url) {$html = str_replace("<a",$rel,$html);}
  return $html;
}
add_filter( \'image_send_to_editor\', \'insert_img_rel_attrib\', 10, 6 );