Development and optimization of PHP blog system

CREATE TABLE `user` (
  `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `username` varchar(255) NOT NULL,
  `password` varchar(255) NOT NULL,
  `email` varchar(255) NOT NULL
);

CREATE TABLE `category` (
  `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `name` varchar(255) NOT NULL
);

CREATE TABLE `article` (
  `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `title` varchar(255) NOT NULL,
  `content` text NOT NULL,
  `category_id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  `created_at` datetime NOT NULL,
  `updated_at` datetime NOT NULL,
  FOREIGN KEY (`category_id`) REFERENCES category(`id`),
  FOREIGN KEY (`user_id`) REFERENCES user(`id`)
);

CREATE TABLE `comment` (
  `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `content` text NOT NULL,
  `article_id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  `created_at` datetime NOT NULL,
  FOREIGN KEY (`article_id`) REFERENCES article(`id`),
  FOREIGN KEY (`user_id`) REFERENCES user(`id`)
);

// user.php
class UserController {
  public function login() {
    // 用户登录逻辑处理
    // ...
    // 页面渲染
    include 'login.html';
  }
  
  public function register() {
    // 用户注册逻辑处理
    // ...
    // 页面渲染
    include 'register.html';
  }
}

// article.php
class ArticleController {
  public function create() {
    // 创建文章逻辑处理
    // ...
    // 页面渲染
    include 'create_article.html';
  }
  
  public function edit() {
    // 编辑文章逻辑处理
    // ...
    // 页面渲染
    include 'edit_article.html';
  }
}

// category.php
class CategoryController {
  public function create() {
    // 创建分类逻辑处理
    // ...
    // 页面渲染
    include 'create_category.html';
  }
  
  public function edit() {
    // 编辑分类逻辑处理
    // ...
    // 页面渲染
    include 'edit_category.html';
  }
}

// comment.php
class CommentController {
  public function create() {
    // 创建评论逻辑处理
    // ...
    // 页面渲染
    include 'create_comment.html';
  }
  
  public function edit() {
    // 编辑评论逻辑处理
    // ...
    // 页面渲染
    include 'edit_comment.html';
  }
}

// 增加索引
CREATE INDEX idx_article_user_id ON `article` (`user_id`);

// 优化SQL语句
SELECT * FROM `article` WHERE `user_id` = 1 ORDER BY `created_at` DESC LIMIT 10;

// 使用缓存
function getArticlesByUserId($userId) {
  $cacheKey = 'articles_' . $userId;
  $articles = cache_get($cacheKey);
  if (!$articles) {
    $articles = db_query("SELECT * FROM `article` WHERE `user_id` = " . $userId);
    cache_set($cacheKey, $articles);
  }
  return $articles;
}

function renderHomePage() {
  $cacheKey = 'home_page';
  $html = cache_get($cacheKey);
  if (!$html) {
    // 业务逻辑处理
    $articles = getLatestArticles();
    $html = render('home.html', ['articles' => $articles]);
    cache_set($cacheKey, $html);
  }
  echo $html;
}

// 使用变量缓存重复计算结果
$array = [1, 2, 3, 4, 5];
$sum = array_sum($array); // 每次都重新计算
echo $sum;

$sum = 0;
foreach ($array as $value) {
  $sum += $value;
}
echo $sum;

// 合并多个SQL查询
SELECT COUNT(*) FROM `article` WHERE `category_id` = 1;
SELECT * FROM `article` WHERE `category_id` = 1 LIMIT 10;

SELECT * FROM `article` WHERE `category_id` = 1; // 只查询一次，然后在代码中分别处理

// 使用缓存控制
header('Cache-Control: max-age=3600'); // 设置浏览器缓存时间