帝国CMS 自动增加标题首尾汉字到指定字段

$sql=$empire->query("select title,id from {$dbtbpre}ecms_news where id>0");
while ($row=$empire->fetch($sql)) {
  $tou=mb_substr($row[title],0,1,'utf-8'); //获取标题头一个字
  //$wei=mb_substr($row[title],mb_strlen($str,'utf-8')-1,1,'utf-8'); //获取标题最后一个字
  $empire->fetch1("update {$dbtbpre}ecms_news set tou = '$tou' where id = $row[id]");
  echo $row['id'];        
}