php 用面向对象的方法对数据库增删改查

<?php
$code = $_POST["code"];
$name = $_POST["name"];
$sex = $_POST["sex"];
$nation = $_POST["nation"];
$birthday = $_POST["birthday"];

$db = new MySQLi("localhost","root","123","mydb");
$sql = "update Info set Name='{$name}',Sex={$sex},Nation='{$nation}',Birthday='{$birthday}' where Code='{$code}' ";

$r = $db->query($sql);

if($r)
{
header("location:main.php");
}
else
{
echo "修改失败！";
}