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php实现多级评论

2026-02-15 07:31:12PHP

实现多级评论的数据库设计

多级评论通常采用自关联表结构。创建一个comments表，包含以下字段：

CREATE TABLE comments (
    id INT AUTO_INCREMENT PRIMARY KEY,
    content TEXT NOT NULL,
    user_id INT NOT NULL,
    parent_id INT DEFAULT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (parent_id) REFERENCES comments(id) ON DELETE CASCADE
);

parent_id字段指向父级评论的ID，顶级评论的parent_id为NULL。

递归查询评论数据

使用递归CTE查询多级评论（MySQL 8.0+）：

WITH RECURSIVE comment_tree AS (
    SELECT id, content, user_id, parent_id, created_at, 0 AS depth
    FROM comments
    WHERE parent_id IS NULL

    UNION ALL

    SELECT c.id, c.content, c.user_id, c.parent_id, c.created_at, ct.depth + 1
    FROM comments c
    JOIN comment_tree ct ON c.parent_id = ct.id
)
SELECT * FROM comment_tree ORDER BY depth, created_at;

PHP处理递归数据

对于不支持递归CTE的MySQL版本，可以在PHP中处理递归：

function buildCommentTree($parentId = null, $depth = 0) {
    $comments = [];
    $stmt = $pdo->prepare("SELECT * FROM comments WHERE parent_id " . 
                         ($parentId === null ? "IS NULL" : "= ?"));
    $params = $parentId === null ? [] : [$parentId];
    $stmt->execute($params);

    while ($comment = $stmt->fetch(PDO::FETCH_ASSOC)) {
        $comment['replies'] = buildCommentTree($comment['id'], $depth + 1);
        $comments[] = $comment;
    }

    return $comments;
}

前端展示嵌套评论

使用HTML和CSS展示多级评论结构：

<div class="comments">
    <?php foreach ($commentTree as $comment): ?>
        <div class="comment" style="margin-left: <?= $comment['depth'] * 30 ?>px">
            <p><?= htmlspecialchars($comment['content']) ?></p>
            <button class="reply-btn" data-comment-id="<?= $comment['id'] ?>">回复</button>

            <?php if (!empty($comment['replies'])): ?>
                <?php include 'comments_partial.php' ?>
            <?php endif; ?>
        </div>
    <?php endforeach; ?>
</div>

AJAX添加新评论

使用jQuery处理评论提交：

$('.reply-btn').click(function() {
    const parentId = $(this).data('comment-id');
    $('#parent_id').val(parentId);
    $('#comment-form').show();
});

$('#comment-form').submit(function(e) {
    e.preventDefault();
    $.post('/add_comment.php', $(this).serialize(), function(response) {
        location.reload();
    });
});

性能优化建议

对于大型评论系统，考虑以下优化措施：

添加path字段存储评论路径（如"1/4/7"表示ID为7的评论的父路径）
为parent_id字段添加索引
实现分页加载评论
使用缓存减少数据库查询

完整示例代码

处理评论提交的PHP代码：

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $content = trim($_POST['content']);
    $userId = (int)$_SESSION['user_id'];
    $parentId = isset($_POST['parent_id']) ? (int)$_POST['parent_id'] : null;

    $stmt = $pdo->prepare("INSERT INTO comments (content, user_id, parent_id) VALUES (?, ?, ?)");
    $stmt->execute([$content, $userId, $parentId]);

    header('Location: ' . $_SERVER['HTTP_REFERER']);
    exit;
}

php实现多级评论