PHP实现的在线投票系统的用户隐私保护

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

// 连接数据库
$conn = new mysqli($servername, $username, $password, $dbname);

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

// 用户登录函数
function login($username, $password) {
    global $conn;
    // 防止SQL注入攻击
    $username = mysqli_real_escape_string($conn, $username);
    $password = mysqli_real_escape_string($conn, $password);
    // 查询用户是否存在
    $sql = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";
    $result = $conn->query($sql);
    if ($result->num_rows > 0) {
        // 登录成功
        return true;
    }
    // 登录失败
    return false;
}

// 投票函数
function vote($username, $option) {
    global $conn;
    // 查询用户是否已经投过票
    $sql = "SELECT * FROM votes WHERE username = '$username'";
    $result = $conn->query($sql);
    if ($result->num_rows > 0) {
        // 用户已经投过票
        return false;
    }
    // 插入投票记录
    $sql = "INSERT INTO votes (username, option) VALUES ('$username', '$option')";
    if($conn->query($sql) === TRUE) {
        // 投票成功
        return true;
    }
    // 投票失败
    return false;
}

// 关闭数据库连接
$conn->close();
?>