PHP と PHPMAILER を探索する: 電子メールに購読行動統計を実装するにはどうすればよいですか?

CREATE TABLE `subscribers` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `email` varchar(255) NOT NULL,
  `subscribe_date` datetime NOT NULL,
  `unsubscribe_date` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

require 'path/to/PHPMailerAutoload.php';

// 连接到数据库
$pdo = new PDO('mysql:host=localhost;dbname=subscription', 'username', 'password');
$pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);

// 获取邮件订阅者信息
$email = $_POST['email'];

// 插入订阅者信息到数据库
$stmt = $pdo->prepare('INSERT INTO subscribers (email, subscribe_date) VALUES (?, NOW())');
$stmt->execute([$email]);

// 发送订阅邮件
$mail = new PHPMailer;

$mail->isSMTP();
$mail->Host = 'smtp.gmail.com';
$mail->SMTPAuth = true;
$mail->Username = 'your-email@gmail.com';
$mail->Password = 'your-password';
$mail->SMTPSecure = 'tls';
$mail->Port = 587;

$mail->From = 'your-email@gmail.com';
$mail->FromName = 'Your Name';
$mail->addAddress($email);

$mail->isHTML(true);

$mail->Subject = 'Subscription Confirmation';
$mail->Body    = 'Thank you for subscribing to our newsletter.';

if(!$mail->send()) {
    echo 'Message could not be sent.';
    echo 'Mailer Error: ' . $mail->ErrorInfo;
} else {
    echo 'Message has been sent.';
}

$tracking_code = md5(uniqid(rand(), true));
$tracking_link = 'http://your-website.com/tracking.php?code=' . $tracking_code;

$mail->Body = 'Thank you for subscribing to our newsletter. Please click <a href="' . $tracking_link . '">here</a> to confirm your subscription.';

$code = $_GET['code'];

$stmt = $pdo->prepare('UPDATE subscribers SET subscribe_date = NOW() WHERE MD5(CONCAT(id,email)) = ?');
$stmt->execute([$code]);

echo 'Subscription confirmed!';