PHP+mysql 计算文本字段的数字合计值,保留小数点2位

<?php
//PHP+mysql 计算文本字段的合计值,并小数点

$dbhost = "localhost";		//数据库地址本地localhost
$dbuser = "******";	//数据库账号
$dbpass = "********";	//数据库密码
$dbname = "******";	//数据库名称
$dbport = "3306";		//数据库端口号
$dbcode = "UTF8";		//数据库编码  UTF8 GB2312
$biaoge = "biao";		//无效：数据库的表名称=chalide_二级域名
$toduan = "******"; //计算字段名称
//修改以上参数

$conn = mysqli_connect($dbhost, $dbuser, $dbpass, $dbname, $dbport);
if (!$conn){ die("连接失败: " . mysqli_connect_error()); }

$sql = "SELECT SUM(CAST(`$toduan` AS DECIMAL(10,2))) AS sum FROM `{$biaoge}`";
$result = $conn->query($sql);
while($row = $result->fetch_assoc()){ echo "合计:".$row["sum"];}
$conn->close();