온라인 질의응답 기능을 위한 사용자 등록 및 로그인 구현 방법

<?php
// 连接数据库
$connect = mysqli_connect("localhost", "username", "password", "database");

// 获取用户提交的注册信息
$username = $_POST['username'];
$password = $_POST['password'];
$email = $_POST['email'];

// 检查用户名是否已经存在
$query = "SELECT username FROM users WHERE username = '$username'";
$result = mysqli_query($connect, $query);
if (mysqli_num_rows($result) > 0) {
    echo "该用户名已被注册";
    exit;
}

// 插入用户信息到数据库
$query = "INSERT INTO users (username, password, email) VALUES ('$username', '$password', '$email')";
$result = mysqli_query($connect, $query);

if ($result) {
    echo "注册成功";
} else {
    echo "注册失败";
}

// 关闭数据库连接
mysqli_close($connect);
?>

<?php
// 连接数据库
$connect = mysqli_connect("localhost", "username", "password", "database");

// 获取用户提交的登录信息
$username = $_POST['username'];
$password = $_POST['password'];

// 检查用户名和密码是否匹配
$query = "SELECT id, username FROM users WHERE username = '$username' AND password = '$password'";
$result = mysqli_query($connect, $query);
if (mysqli_num_rows($result) > 0) {
    // 将用户信息保存在会话中
    session_start();
    $_SESSION['loggedin'] = true;
    $_SESSION['username'] = $username;

    // 登录成功跳转到答题页面
    header("Location: quiz.php");
} else {
    echo "用户名或密码错误";
}

// 关闭数据库连接
mysqli_close($connect);
?>