Bagaimana untuk menggunakan PHP untuk melaksanakan fungsi peringatan tempoh langganan e-mel?

CREATE TABLE subscribers (
  id INT PRIMARY KEY AUTO_INCREMENT,
  email VARCHAR(255) NOT NULL,
  timezone VARCHAR(255) NOT NULL,
  preference VARCHAR(255) NOT NULL
);

<form action="subscribe.php" method="post">
  <input type="email" name="email" placeholder="请输入邮箱地址" required>
  <select name="timezone" required>
    <option value="GMT-12:00">国际日期变更线西</option>
    <option value="GMT-11:00">夏威夷标准时间</option>
    <!-- 其他时区选项 -->
  </select>
  <input type="checkbox" name="preference[]" value="morning">早上
  <input type="checkbox" name="preference[]" value="afternoon">下午
  <input type="checkbox" name="preference[]" value="evening">晚上
  <input type="submit" value="订阅">
</form>

<?php
// 连接数据库
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";
$conn = new mysqli($servername, $username, $password, $dbname);

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

// 获取用户提交的表单数据
$email = $_POST['email'];
$timezone = $_POST['timezone'];
$preferences = $_POST['preference'];

// 将数据插入到数据库中
$sql = "INSERT INTO subscribers (email, timezone, preference) VALUES ('$email', '$timezone', '" . serialize($preferences) . "')";

if ($conn->query($sql) === TRUE) {
  echo "订阅成功!";
} else {
  echo "订阅失败: " . $conn->error;
}

// 关闭数据库连接
$conn->close();
?>

<?php
// 连接数据库
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";
$conn = new mysqli($servername, $username, $password, $dbname);

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

// 获取当前时间
$current_time = date('H:i');

// 查询订阅者列表
$sql = "SELECT * FROM subscribers";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
  while($row = $result->fetch_assoc()) {
    // 检查是否在用户指定的提醒时段内
    $preferences = unserialize($row['preference']);
    if (in_array($current_time, $preferences)) {
      // 发送邮件提醒订阅者
      $to = $row['email'];
      $subject = "邮件订阅提醒";
      $message = "这是一封邮件订阅提醒。";
      $headers = "From: your_email@example.com";

      mail($to, $subject, $message, $headers);
    }
  }
}

// 关闭数据库连接
$conn->close();
?>