php如何调用更改邮箱的验证

<?php
// 数据库连接
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 生成验证令牌
$token = bin2hex(random_bytes(32));

// 假设用户ID为1，旧邮箱为old@example.com，新邮箱为new@example.com
$user_id = 1;
$old_email = "old@example.com";
$new_email = "new@example.com";

// 将令牌和邮箱信息插入数据库
$sql = "INSERT INTO email_verification (user_id, old_email, new_email, token, created_at)
VALUES ('$user_id', '$old_email', '$new_email', '$token', NOW())";

if ($conn->query($sql) === TRUE) {
    // 发送验证邮件
    $to = $old_email;
    $subject = "邮箱更改验证";
    $message = "点击以下链接验证您的邮箱更改：\n\nhttp://example.com/verify_email.php?token=$token";
    $headers = "From: webmaster@example.com";

    mail($to, $subject, $message, $headers);
    echo "验证邮件已发送";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>