php - 在选择查询中使用变量

Question

问题
我正在尝试创建一个网站，用户可以在其中发布帖子，然后他们的 friend 可以看到这些帖子。类似于 facebook, twitter 等
我已经到了用户可以成为 friend 并且他们可以发布内容的地步。但是，我无法将显示的帖子限制为仅显示用户 friend 的帖子。目前每个用户都可以看到每个帖子。
我在 MVC 架构中使用 PDO。

数据库结构

TABLE `friends` (
    `friendship_id` int(11) NOT NULL AUTO_INCREMENT,
    `user_one` int(11) NOT NULL,
    `user_two` int(11) NOT NULL,
    PRIMARY KEY (`friendship_id`),
    FOREIGN KEY (user_one) REFERENCES users(user_id),
    FOREIGN KEY (user_two) REFERENCES users(user_id)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

在上表中，根据谁向谁发送了好友请求，“user_one”可以是我自己或我的 friend ，或者“user_two”可以是我自己或我的 friend 。

TABLE `posts` (
 `post_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
 `post_text` text NOT NULL,
 `user_id` int(11) unsigned NOT NULL,
 PRIMARY KEY (`post_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

模型

    /**
     * Get all posts from the suer's friends
     * @return array an array with several objects (the posts)
     */
    public static function getAllPosts()
    {   
        $my_id = Session::get('user_id');

        $database = DatabaseFactory::getFactory()->getConnection();

        // get all of the user's friends
        $friendsQuery = $database->prepare("
                                    SELECT user_one FROM friends WHERE user_two = '$my_id';
                                    SELECT user_two FROM friends WHERE user_one = '$my_id';
                                    ");

        $friendsQuery->execute();
        $friends = $friendsQuery->fetchAll();
        $friendsQuery->closeCursor();

        $query = $database->prepare("SELECT * FROM posts WHERE user_id = '$my_id' OR user_id = '$friends'");
        $query->execute(array());

        return $query->fetchAll();
    }

在上面的代码中，我的问题在于 $friends 变量。如果我用我 friend 的 user_id 手动替换它，它会按预期工作。
例如:

"SELECT * FROM posts WHERE user_id = '$my_id' OR user_id = '1'"; 

Controller

    /**
     * Gets all posts (of the user and his friends).
     */
    public function index()
    {
        $this->View->render('post/index', array(
            'posts' => PostModel::getAllPosts()
        ));
    }

View

       <?php if ($this->posts) { ?>
            <?php foreach($this->posts as $key => $value) { ?>
                <p><?= htmlentities($value->post_text); ?></p>
            <?php } ?>
        <?php } ?>

总结
我无法创建一个 sql 查询，它只选择由我自己或我的 friend 发布的帖子，而不选择任何其他帖子。

如果有人能帮我解决这个问题，我将不胜感激!

更新
我的模型现在看起来像这样:

    /**
     * Get all posts from the suer's friends
     * @return array an array with several objects (the posts)
     */
    public static function getAllPosts()
    {   
        $my_id = Session::get('user_id');

        $database = DatabaseFactory::getFactory()->getConnection();

        // get all of the user's friends
        $friendsQuery = $database->prepare("
                                    SELECT user_one FROM friends WHERE user_two = '$my_id';
                                    SELECT user_two FROM friends WHERE user_one = '$my_id';
                                    ");

        $friendsQuery->execute();
        $friends = $friendsQuery->fetchAll();
        print_r($friends);
        $friendsQuery->closeCursor();

        foreach($friends as $friend)
        {
            $friend_ids[$friend->key] = $friend->val;
        }
        print_r($friend_ids);
        $friendsSQL = implode(',',$friend_ids);

        $query = $database->prepare("SELECT * FROM posts WHERE user_id = '$my_id' OR user_id IN('$friendsSQL')");
        $query->execute();

        return $query->fetchAll();
    }

这是我的输出:

Array ( [0] => stdClass Object ( [user_one] => 1 ) )

Notice: Undefined property: stdClass::$key

Notice: Undefined property: stdClass::$val

Array ( [] => )

Answer 1

您可以将所有 friends_id 添加到一个数组中，然后使用此代码。

//$friends is an array.
$friendsSQL = implode(',',$friends);
$query = $database->prepare("SELECT * FROM posts WHERE user_id = '$my_id' OR user_id IN($friendsSQL)");