PHPでデータベース内のデータを変更する方法

 $sql = "select * from user_info where user_id='".$_GET['userId']."'";
 $result = mysql_query($sql,$con);
 if($row = mysql_fetch_array($result)){
}

//通过post获取页面提交数据信息
$userId = $_POST[userId];
$userName = $_POST[userName];
$userAge = $_POST[userAge];
 
$sql = "update user_info set user_name='".$userName."',user_age=".$userAge." where user_id='".$userId."'";
mysql_query($sql,$conn);//执行SQL
$mark  = mysql_affected_rows();//返回影响行数
$url = "userinf_select.php";

$userId = $_GET['userId'];
 
include 'connection.php';
 
$sql = "delete from user_info where user_id='".$userId."'";
 
mysql_query($sql,$con);
 
$mark  = mysql_affected_rows();//返回影响行数
 
if($mark>0){
 echo "删除成功";
}else{
 echo  "删除失败";
}
 
mysql_close($con);