如何使用PHP开发简单的文章标签和分类功能

<form action="add_article.php" method="POST">
    <input type="text" name="title" placeholder="文章标题"><br><br>
    <textarea name="content" placeholder="文章内容"></textarea><br><br>
    <input type="text" name="tags" placeholder="标签（多个标签用逗号分隔）"><br><br>
    <select name="category">
        <option value="">选择分类</option>
        <!-- 根据分类表动态生成选项 -->
    </select><br><br>
    <input type="submit" value="发布文章">
</form>

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

// 处理提交的数据
$title = $_POST['title'];
$content = $_POST['content'];
$tags = $_POST['tags'];
$category = $_POST['category'];

// 插入文章数据
$result = mysqli_query($conn, "INSERT INTO article (title, content, category_id) VALUES ('$title', '$content', '$category')");

// 获取插入文章的ID
$articleId = mysqli_insert_id($conn);

// 处理标签
$tagArray = explode(",", $tags);
foreach ($tagArray as $tag) {
    $tag = trim($tag);
    // 查询标签是否存在
    $tagResult = mysqli_query($conn, "SELECT id FROM tags WHERE name = '$tag'");
    if (mysqli_num_rows($tagResult) == 0) {
        // 标签不存在，插入新的标签
        mysqli_query($conn, "INSERT INTO tags (name) VALUES ('$tag')");
        // 获取插入标签的ID
        $tagId = mysqli_insert_id($conn);
    } else {
        $tagId = mysqli_fetch_assoc($tagResult)['id'];
    }
    // 插入标签和文章的关联关系
    mysqli_query($conn, "INSERT INTO article_tags (article_id, tag_id) VALUES ($articleId, $tagId)");
}

// 关闭数据库连接
mysqli_close($conn);

// 跳转到文章详情页
header("Location: article.php?id=$articleId");
exit;
?>

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

    // 查询文章数据
    $result = mysqli_query($conn, "SELECT * FROM article");

    // 输出文章列表
    while ($row = mysqli_fetch_assoc($result)) {
        echo "<li><a href='article.php?id=".$row['id']."'>".$row['title']."</a>";
        
        // 查询文章的标签
        echo "<ul>";
        $tagResult = mysqli_query($conn, "SELECT t.name FROM tags t INNER JOIN article_tags at ON t.id = at.tag_id WHERE at.article_id = ".$row['id']);
        while ($tagRow = mysqli_fetch_assoc($tagResult)) {
            echo "<li>".$tagRow['name']."</li>";
        }
        echo "</ul>";

        // 查询文章的分类
        echo "<ul>";
        $categoryResult = mysqli_query($conn, "SELECT c.name FROM categories c WHERE c.id = ".$row['category_id']);
        while ($categoryRow = mysqli_fetch_assoc($categoryResult)) {
            echo "<li>".$categoryRow['name']."</li>";
        }
        echo "</ul>";
        
        echo "</li>";
    }

    // 关闭数据库连接
    mysqli_close($conn);
    ?>
</ul>

<?php
// 获取文章ID
$articleId = $_GET['id'];

// 连接数据库
$conn = mysqli_connect("localhost", "username", "password", "database");

// 查询文章数据
$articleResult = mysqli_query($conn, "SELECT * FROM article WHERE id = $articleId");
$articleRow = mysqli_fetch_assoc($articleResult);

// 查询文章的标签
$tagsResult = mysqli_query($conn, "SELECT t.name FROM tags t INNER JOIN article_tags at ON t.id = at.tag_id WHERE at.article_id = $articleId");

// 查询文章的分类
$categoryResult = mysqli_query($conn, "SELECT c.name FROM categories c WHERE c.id = ".$articleRow['category_id']);
$categoryRow = mysqli_fetch_assoc($categoryResult);

// 关闭数据库连接
mysqli_close($conn);
?>

<h1><?php echo $articleRow['title']; ?></h1>
<p><?php echo $articleRow['content']; ?></p>

<h3>标签</h3>
<ul>
    <?php
    while ($tagRow = mysqli_fetch_assoc($tagsResult)) {
        echo "<li>".$tagRow['name']."</li>";
    }
    ?>
</ul>

<h3>分类</h3>
<ul>
    <li><?php echo $categoryRow['name']; ?></li>
</ul>