数据库删除后台代码

<?php
header( 'Content-Type:text/html;charset=utf-8 ');
 include_once("conn/conn.php");
 $id=$_GET["id"];

 $sql='delete from user where id='.$id;
 $r=mysqli_query($link,$sql);
 if($r){
  echo "成功，点击<a href='index_ok.php'>返回</a>";
 }else{
  echo "<script>alert('删除失败');history.back();</script>";
 }