PHPでデータを一括削除する方法

     例如(list.php):
  <form name="del_form" action="del.php" method="post">
  <?php
        $result=mysql_query("select * from news");
        while($rs=mysql_fetch_array($result)){
     ?>
        <input name="del_id[]" type="checkbox" id="del_id[]" value="<?=$rs[id]?>" /><?=$rs[title]?>
     <?php
        }
     ?>
   </form>

  <?php
     if($del_id!=""){
             $del_num=count($del_id);
             for($i=0;$i<$del_num;$i++){
                 mysql_query("Delete from news where id=&#39;$del_id[$i]&#39;");
             } 
             echo("<script type=&#39;text/javascript&#39;>alert(&#39;删除成功！&#39;);history.back();</script>");
      }else{
             echo("<script type=&#39;text/javascript&#39;>alert(&#39;请先选择项目！&#39;);history.back();</script>");
      }
    ?>