PHP用户认证系统常见陷阱：变量冲突与安全实践指南

<?php
if (isset($_POST["submit"])) {
    $name = $_POST["namee"];
    $email = $_POST["emaill"];
    $username = $_POST["userme"]; // 用户名变量
    $password = $_POST["passme"]; // 密码变量

    require_once 'db.php'; // 在此处包含db.php
    require_once 'functions.php';

    createUser($conn, $name, $email, $username, $password);
}
else {
    header("location: signup.php");
}

<?php
$servername = "localhost";
$username = "root";   // 数据库连接用户名
$password = "password"; // 数据库连接密码
$dbname = "phpshop";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);

// Check connection
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}

<?php
if (isset($_POST["submit"])) {
    // 使用与db.php中不同的变量名来存储用户输入
    $inputName = $_POST["namee"];
    $inputEmail = $_POST["emaill"];
    $inputUsername = $_POST["userme"];
    $inputPassword = $_POST["passme"]; // 这是用户输入的原始密码

    require_once 'db.php';
    require_once 'functions.php';

    // 将用户输入传递给createUser函数
    createUser($conn, $inputName, $inputEmail, $inputUsername, $inputPassword);
} else {
    // 当非POST请求访问时，重定向回注册页面
    echo "<script>window.location.href='signup.php';</script>";
    exit();
}
?>

function createUser($conn, $namee, $emaill, $userme, $passme) {
    // ...
    $hashedPwd = password_hash($passme, PASSWORD_DEFAULT); // 原始代码中包含哈希
    mysqli_stmt_bind_param($stmt, "ssss", $namee, $emaill, $userme, $hashedPwd);
    // ...
}

function createUser($conn, $name, $email, $username, $password) {
    // ...
    // 注意：此处移除了password_hash()，这在实际应用中是安全隐患
    mysqli_stmt_bind_param($stmt, "ssss", $name, $email, $username, $password);
    // ...
}

<?php

function createUser($conn, $name, $email, $username, $password) {
    // 可以在此处添加更严格的输入验证，例如检查空字段、邮箱格式等
    if (empty($name) || empty($email) || empty($username) || empty($password)) {
        echo "<script>alert('所有字段都不能为空。'); window.location.href='signup.php';</script>";
        exit();
    }
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        echo "<script>alert('请输入有效的邮箱地址。'); window.location.href='signup.php';</script>";
        exit();
    }

    $sql = "INSERT INTO GuestsLogs (namee, emaill, userme, passme) VALUES (?, ?, ?, ?);";
    $stmt = mysqli_stmt_init($conn);

    if (!mysqli_stmt_prepare($stmt, $sql)) {
        // 记录错误以便调试，不直接向用户显示敏感信息
        error_log("SQL statement preparation failed for createUser: " . mysqli_error($conn));
        echo "<script>alert('注册失败，请稍后再试。'); window.location.href='signup.php';</script>";
        exit();
    }

    // 使用 password_hash() 对密码进行哈希处理
    $hashedPwd = password_hash($password, PASSWORD_DEFAULT);
    if ($hashedPwd === false) {
        error_log("Password hashing failed.");
        echo "<script>alert('注册失败，请稍后再试。'); window.location.href='signup.php';</script>";
        exit();
    }

    mysqli_stmt_bind_param($stmt, "ssss", $name, $email, $username, $hashedPwd);
    mysqli_stmt_execute($stmt);

    if (mysqli_stmt_errno($stmt)) {
        // 检查是否有唯一约束冲突等数据库错误
        if (mysqli_stmt_errno($stmt) == 1062) { // 1062是MySQL的DUPLICATE ENTRY错误码
            echo "<script>alert('用户名或邮箱已被占用。'); window.location.href='signup.php';</script>";
        } else {
            error_log("SQL statement execution failed for createUser: " . mysqli_stmt_error($stmt));
            echo "<script>alert('注册失败，请稍后再试。'); window.location.href='signup.php';</script>";
        }
        exit();
    }

    mysqli_stmt_close($stmt);
    echo "<script>alert('注册成功！'); window.location.href='index.php';</script>"; // 注册成功后重定向到首页或登录页
    exit();
}

function loginUser($conn, $userme, $passme) {
    $passHashed = ["passme"]; // 错误：这只是一个字符串数组，不是从DB获取的哈希值
    $checkPwd = password_verify($passme, "passme"); // 错误：与硬编码字符串比较

    if ($checkPwd === false) {
        echo "<script>window.location.href='signup.php';</script>";
        exit();
    }
    else if ($checkPwd === true) {
        session_start();
        $_SESSION["userme"] = $passme["userme"]; // 错误：$passme不是数组
        echo "<script>window.location.href='index.php';</script>";
        exit();
    }
}

function loginUser($conn, $username, $password) {
    // 1. 根据用户名从数据库中查找用户记录
    $sql = "SELECT id, userme, passme FROM GuestsLogs WHERE userme = ?;";