Bagaimana untuk menggunakan PHP untuk melaksanakan fungsi pendaftaran log masuk pengesahan e-mel?

CREATE DATABASE `userdb`;
USE `userdb`;

CREATE TABLE `users` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(50) NOT NULL,
  `email` VARCHAR(50) NOT NULL,
  `password` VARCHAR(255) NOT NULL,
  `is_verified` INT(1) NOT NULL DEFAULT '0',
  `verification_code` VARCHAR(255),
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $name = $_POST['name'];
    $email = $_POST['email'];
    $password = $_POST['password'];

    $verification_code = md5(uniqid(rand(), true));

    // 将用户信息插入数据库
    $conn = new mysqli('localhost', 'username', 'password', 'userdb');

    $sql = "INSERT INTO users (name, email, password, verification_code) VALUES ('$name', '$email', '$password', '$verification_code')";
    
    if ($conn->query($sql) === TRUE) {
        // 发送验证邮件
        $subject = "请验证您的邮箱";
        $message = "请点击以下链接完成验证：
";
        $message .= "http://yourdomain.com/verify.php?code=$verification_code";
        $headers = "From: noreply@yourdomain.com";

        mail($email, $subject, $message, $headers);
        echo "注册成功，请前往您的邮箱验证账户！";
    } else {
        echo "注册失败，请稍后再试！";
    }

    $conn->close();
}
?>

<?php
if (isset($_GET['code']) && !empty($_GET['code'])) {
    $verification_code = $_GET['code'];

    $conn = new mysqli('localhost', 'username', 'password', 'userdb');

    $sql = "SELECT id FROM users WHERE verification_code='$verification_code' AND is_verified=0";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        $sql = "UPDATE users SET is_verified=1 WHERE verification_code='$verification_code'";

        if ($conn->query($sql) === TRUE) {
            echo "验证成功！";
        } else {
            echo "验证失败，请稍后再试！";
        }
    } else {
        echo "无效的验证码！";
    }

    $conn->close();
}
?>

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $email = $_POST['email'];
    $password = $_POST['password'];

    $conn = new mysqli('localhost', 'username', 'password', 'userdb');

    $sql = "SELECT id FROM users WHERE email='$email' AND password='$password' AND is_verified=1";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        echo "登录成功！";
    } else {
        echo "登录失败，请检查邮箱和密码是否正确，或者邮箱是否已验证！";
    }

    $conn->close();
}
?>