构建一个安全可靠的PHP在线投票平台

id INT(11) PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(50) NOT NULL,
password VARCHAR(100) NOT NULL

id INT(11) PRIMARY KEY AUTO_INCREMENT,
title VARCHAR(100) NOT NULL,
description TEXT NOT NULL

id INT(11) PRIMARY KEY AUTO_INCREMENT,
poll_id INT(11) NOT NULL,
option_text VARCHAR(200) NOT NULL,
votes INT(11) DEFAULT 0

id INT(11) PRIMARY KEY AUTO_INCREMENT,
user_id INT(11) NOT NULL,
poll_id INT(11) NOT NULL,
option_id INT(11) NOT NULL,
FOREIGN KEY (user_id) REFERENCES users(id),
FOREIGN KEY (poll_id) REFERENCES polls(id),
FOREIGN KEY (option_id) REFERENCES options(id)

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $username = $_POST['username'];
    $password = password_hash($_POST['password'], PASSWORD_DEFAULT);
    
    // 将用户名和密码插入至数据库
    $sql = "INSERT INTO users (username, password) VALUES ('$username', '$password')";
    // 执行插入操作
    $result = mysqli_query($conn, $sql);
    
    if ($result) {
        echo "注册成功！";
    } else {
        echo "注册失败，请重试！";
    }
}
?>

<form action="register.php" method="POST">
    <input type="text" name="username" placeholder="用户名" required>
    <input type="password" name="password" placeholder="密码" required>
    <button type="submit">注册</button>
</form>

<?php
session_start();

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $username = $_POST['username'];
    $password = $_POST['password'];
    
    // 根据用户名查询数据库
    $sql = "SELECT * FROM users WHERE username='$username'";
    $result = mysqli_query($conn, $sql);
    $user = mysqli_fetch_assoc($result);
    
    if ($user && password_verify($password, $user['password'])) {
        $_SESSION['user_id'] = $user['id'];
        $_SESSION['username'] = $user['username'];
        header("Location: dashboard.php");
    } else {
        echo "用户名或密码错误！";
    }
}
?>

<form action="login.php" method="POST">
    <input type="text" name="username" placeholder="用户名" required>
    <input type="password" name="password" placeholder="密码" required>
    <button type="submit">登录</button>
</form>

<?php
session_start();

if ($_SERVER['REQUEST_METHOD'] == 'POST' && isset($_SESSION['user_id'])) {
    $title = $_POST['title'];
    $description = $_POST['description'];
    $options = $_POST['options'];
    
    // 插入投票主题表
    $sql = "INSERT INTO polls (title, description) VALUES ('$title', '$description')";
    mysqli_query($conn, $sql);
    $poll_id = mysqli_insert_id($conn);
    
    foreach ($options as $option) {
        // 插入选项表
        $sql = "INSERT INTO options (poll_id, option_text) VALUES ('$poll_id', '$option')";
        mysqli_query($conn, $sql);
    }
    
    echo "投票主题创建成功！";
}
?>

<form action="create_poll.php" method="POST">
    <input type="text" name="title" placeholder="投票标题" required>
    <textarea name="description" placeholder="投票描述" required></textarea>
    <label>选项1：<input type="text" name="options[]" required></label>
    <label>选项2：<input type="text" name="options[]" required></label>
    <button type="submit">创建投票</button>
</form>

<?php
session_start();

if (isset($_SESSION['user_id'])) {
    // 查询所有投票主题
    $sql = "SELECT * FROM polls";
    $result = mysqli_query($conn, $sql);
    $polls = mysqli_fetch_all($result, MYSQLI_ASSOC);
    
    foreach ($polls as $poll) {
        echo "<h3>" . $poll['title'] . "</h3>";
        echo "<p>" . $poll['description'] . "</p>";
        
        // 查询选项列表
        $sql = "SELECT * FROM options WHERE poll_id=" . $poll['id'];
        $result = mysqli_query($conn, $sql);
        $options = mysqli_fetch_all($result, MYSQLI_ASSOC);
        
        foreach ($options as $option) {
            echo "<label><input type='radio' name='option' value='" . $option['id'] . "'> " . $option['option_text'] . "</label>";
        }
        
        echo "<button type='submit'>投票</button>";
        echo "<hr>";
    }
} else {
    echo "请先登录！";
}
?>