PHP 实现知识问答网站中的标签管理和推荐功能。

CREATE TABLE `tag` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
);

CREATE TABLE `question` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(100) NOT NULL,
  `content` text NOT NULL,
  PRIMARY KEY (`id`)
);

// 获取用户输入的标签和问题信息
$tags = $_POST['tags'];
$title = $_POST['title'];
$content = $_POST['content'];

// 插入问题信息
$query = "INSERT INTO question (title, content) VALUES ('$title', '$content')";
mysql_query($query);

// 插入标签信息
$questionId = mysql_insert_id();
foreach ($tags as $tag) {
    $query = "INSERT INTO tag (name, question_id) VALUES ('$tag', '$questionId')";
    mysql_query($query);
}

$tag = $_GET['tag'];

$query = "SELECT q.* FROM question q
            INNER JOIN tag t ON q.id = t.question_id
            WHERE t.name = '$tag'";
$result = mysql_query($query);

while ($row = mysql_fetch_assoc($result)) {
    echo $row['title'], "<br/>";
}

$userId = $_SESSION['user_id'];

$query = "SELECT t.name FROM tag t
            INNER JOIN question q ON t.question_id = q.id
            WHERE q.user_id = '$userId'";
$result = mysql_query($query);

while ($row = mysql_fetch_assoc($result)) {
    echo $row['name'], "<br/>";
}

$tags = implode(",", $userTags);

$query = "SELECT * FROM question
            WHERE id NOT IN (SELECT t.question_id FROM tag t
                              WHERE t.name IN ($tags))
            LIMIT 5";
$result = mysql_query($query);

while ($row = mysql_fetch_assoc($result)) {
    echo $row['title'], "<br/>";
}