php中的数据修改mysql数据库连接

<?php
try {
    // 创建PDO实例
    $pdo = new PDO('mysql:host=localhost;dbname=testdb;charset=utf8', 'username', 'password');

    // 设置错误模式为异常
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 插入数据示例
    $stmt = $pdo->prepare("INSERT INTO users (username, email) VALUES (:username, :email)");
    $stmt->bindParam(':username', $username);
    $stmt->bindParam(':email', $email);
    $username = 'JohnDoe';
    $email = 'john@example.com';
    $stmt->execute();

    // 更新数据示例
    $stmt = $pdo->prepare("UPDATE users SET email = :email WHERE username = :username");
    $stmt->bindParam(':email', $newEmail);
    $stmt->bindParam(':username', $username);
    $newEmail = 'john_new@example.com';
    $stmt->execute();

    echo "数据修改成功！";
} catch (PDOException $e) {
    echo "数据库连接失败: " . $e->getMessage();
}
?>