php判断域名可以连接数据库

<?php
function checkDomainConnectivity($domain, $port, $username, $password, $dbname) {
    // DNS解析检查
    if (!checkdnsrr($domain, 'A')) {
        return "DNS解析失败";
    }

    // 端口连接检查
    $fp = @fsockopen($domain, $port, $errno, $errstr, 30);
    if (!$fp) {
        return "无法连接到端口 $port: $errstr ($errno)";
    }
    fclose($fp);

    // 数据库连接检查
    $mysqli = new mysqli($domain, $username, $password, $dbname);
    if ($mysqli->connect_error) {
        return "数据库连接失败: " . $mysqli->connect_error;
    } else {
        $mysqli->close();
        return "连接成功";
    }
}

// 使用示例
$domain = 'example.com';
$port = 3306;
$username = 'dbuser';
$password = 'dbpass';
$dbname = 'dbname';

$result = checkDomainConnectivity($domain, $port, $username, $password, $dbname);
echo $result;
?>