update 的封装方法

<?php
$mysqli=new mysqli("localhost","root","","demo");

if($mysqli->connect_error){
die("连接数据库失败！".$mysqli->connect_error());
}
echo "ok<br/>";

update($mysqli,"student","stuname='小明' where id=888888");
function update($tmysqli,$table,$tiaojian){

$sql="update $table set $tiaojian";
if($tmysqli->query($sql)===true){
echo "修改成功！";

}

}


?>