php函数与数据库交互中的困难解析与修复

<?php // 连接 MySQL 数据库$mysqli = new mysqli("localhost", "username", "password", "database_name");// 检查连接是否成功if ($mysqli->connect_errno) {    echo "连接失败：".$mysqli-&gt;connect_error;} else {    echo "连接成功";}// 关闭连接$mysqli-&gt;close();?&gt;