PHP MYSQL嵌套连接

<?php
// 主数据库连接
$host = "主数据库连接信息";
$user = "用户名";
$password = "密码";
$dbName = "数据库名";

$mainConn = new mysqli($host, $user, $password, $dbName);

// 检查主数据库连接是否成功
if ($mainConn->connect_error) {
    die("主数据库连接失败: " . $mainConn->connect_error);
}

// 嵌套数据库连接
$nestedHost = "嵌套数据库连接信息";
$nestedUser = "用户名";
$nestedPassword = "密码";
$nestedDbName = "数据库名";

$nestedConn = new mysqli($nestedHost, $nestedUser, $nestedPassword, $nestedDbName);

// 检查嵌套数据库连接是否成功
if ($nestedConn->connect_error) {
    die("嵌套数据库连接失败: " . $nestedConn->connect_error);
}

// 执行查询操作
$query = "SELECT * FROM table_name";
$result = $mainConn->query($query);

// 处理查询结果
if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        // 处理每一行数据
        // ...
    }
} else {
    echo "查询结果为空";
}

// 关闭数据库连接
$result->close();
$nestedConn->close();
$mainConn->close();
?>