使用 PHP 开发知识问答网站中的用户密保问题和安全设置功能。

<?php
// 在数据库中创建一个 users 表，用于存储用户信息
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败：" . $conn->connect_error);
}

// 创建 users 表
$sql = "CREATE TABLE users (
    id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(30) NOT NULL,
    password VARCHAR(30) NOT NULL,
    question VARCHAR(100) NOT NULL,
    answer VARCHAR(100) NOT NULL
)";

if ($conn->query($sql) === TRUE) {
    echo "users 表创建成功";
} else {
    echo "创建 users 表时出错：" . $conn->error;
}

// 注册新用户
$username = "johnsmith";
$password = "password123";
$question = "您的出生地是？";
$answer = "纽约";

$sql = "INSERT INTO users (username, password, question, answer)
VALUES ('$username', '$password', '$question', '$answer')";

if ($conn->query($sql) === TRUE) {
    echo "新用户注册成功";
} else {
    echo "注册新用户时出错：" . $conn->error;
}

// 验证用户的密保问题和答案
$login_username = "johnsmith";
$login_answer = "纽约";

$sql = "SELECT * FROM users WHERE username='$login_username' AND answer='$login_answer'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    echo "密保问题和答案验证成功";
} else {
    echo "密保问题和答案验证失败";
}

$conn->close();
?>