php如何实现批量删除数据

<form id="form2" name="form2" method="post" action="del_product.php">
 <label>
 <input type="checkbox" name="id[]" value="1" style="background:none; border:none;" />
 1
 </label>
 <label>
 <input type="checkbox" name="id[]" value="2" style="background:none; border:none;" />
 2
 </label>
 <label>
 <input type="checkbox" name="id[]" value="3" style="background:none; border:none;" />
 3
 </label>
 <label>
 <input type="checkbox" name="id[]" value="4" style="background:none; border:none;" />
 4
 </label>
 <label>
 <input type="checkbox" name="id[]" value="5" style="background:none; border:none;" />
 5
 </label>
 <div style="padding-left:20px;">
 <input type="button" value="全选" style="background:url(images/cheall.jpg) no-repeat; width:60px; height:23px; border:none;" onClick="selectBox('all')"/>
 <input type="button" value="反选" style="background:url(images/cheall.jpg) no-repeat; width:60px; height:23px; border:none;" onClick="selectBox('reverse')"/>
 <input type="submit" name="btnSave" style="background:url(images/cheall.jpg) no-repeat; width:60px; height:23px; border:none;" value="删除"/>
 </div>
</form>

if($_POST['btnSave']){
 if(empty($_POST['id'])){
 echo"<script>alert('必须选择一个产品,才可以删除!');history.back(-1);</script>";
 exit;
 } else {
 /*如果要获取全部数值则使用下面代码*/
 $id= implode(",",$_POST['id']);
 $str="DELETE FROM `product` where id in ($id)";
 mysql_query($str);
 echo "<script>alert('删除成功！');window.location.href='product_list.php';</script>";
 }
}