PHP进阶：前后端交互、cookie验证、sql与php

<?php
// 假设已经连接数据库
 
// 用户登录验证
function login($username, $password) {
    global $pdo;
 
    // 准备SQL语句
    $sql = "SELECT * FROM users WHERE username = :username AND password = :password";
    $stmt = $pdo->prepare($sql);
 
    // 绑定参数
    $stmt->bindParam(':username', $username);
    $stmt->bindParam(':password', $password);
 
    // 执行查询
    $stmt->execute();
 
    // 检查结果
    if ($stmt->rowCount() > 0) {
        // 用户名和密码匹配，登录成功
        return true;
    } else {
        // 登录失败
        return false;
    }
}
 
// 用户注册
function register($username, $password) {
    global $pdo;
 
    // 准备SQL语句
    $sql = "INSERT INTO users (username, password) VALUES (:username, :password)";
    $stmt = $pdo->prepare($sql);
 
    // 绑定参数
    $stmt->bindParam(':username', $username);
    $stmt->bindParam(':password', $password);
 
    // 执行查询
    $stmt->execute();
 
    // 检查结果
    if ($stmt->rowCount() > 0) {
        // 注册成功
        return true;
    } else {
        // 注册失败
        return false;
    }
}
 
// 用户登出
function logout() {
    // 删除cookie
    if (isset($_COOKIE['user_id'])) {
        setcookie('user_id', '', time() - 3600, '/');
    }
}
 
// 检查用户是否登录
function checkLogin() {
    if (isset($_COOKIE['user_id'])) {
        // 用户ID存在于cookie中
        return true;
    } else {
        // 用户未登录
        return false;
    }
}
 
// 用户登录后设置cookie
function setUserCookie($user_id) {
    // 设置cookie
    $expire = time() + (3600 * 24 * 30); // 有效期30天
    setcookie('user_id', $user_id, $expire, '/');
}
 
// 使用示例
if ($_SERVER['REQUEST_METHOD'] == 'POST' && isset($_POST['action'])) {
    $action = $_POST['action'];
    switch ($action) {
        case 'login':
            $username = $_POST['username'];
            $password = $_POST['password'];
            if (login($username, $password)) {
                // 登录成功，设置cookie
                $user_id = 1; // 假设从数据库获取用户ID
                setUserCookie($user_id);
                echo json_encode(['status' => 'success', 'message' => '登录成功']);
            } else {
                echo json_encode(['status' => 'error', 'message' => '登录失败']);
            }
            break;
        case 'register':
            $username = $_POST['username'];
            $password = $_POST['password'];
            if (register($username, $password)) {
                echo json_encode(['status' => 'success', 'message' => '注册成功']);
            } else