如何判断php连接mysql数据库

<?php
// 连接MySQL数据库
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";
 
// 使用mysqli连接MySQL数据库
$conn = mysqli_connect($servername, $username, $password, $dbname);
if (!$conn) {
    die("连接失败: " . mysqli_connect_error());
}
echo "连接成功";

// 使用PDO连接MySQL数据库
try {
    $dsn = "mysql:host=$servername;dbname=$dbname";
    $pdo = new PDO($dsn, $username, $password);
    echo "连接成功";
} catch (PDOException $e) {
    die("连接失败: " . $e->getMessage());
}