PHP + MySQL 實現論壇階層式回覆與分頁顯示：遞迴函數、樹狀結構渲染完整範例

資料表設計：鄰接清單模型

CREATE TABLE bbsrow (
    bbsrow_id       INT(6) NOT NULL AUTO_INCREMENT PRIMARY KEY,
    bbsrow_auth     VARCHAR(20) NOT NULL,
    bbsrow_parentid INT(6) DEFAULT NULL,      -- 父文章 ID，NULL 為主題文
    bbsrow_title    VARCHAR(200) NOT NULL,
    bbsrow_returncount INT(3) DEFAULT NULL,   -- 回覆數統計
    bbsrow_content  TEXT,                     -- 文章內容
    bbsrow_posttime DATETIME DEFAULT CURRENT_TIMESTAMP
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

核心邏輯：遞迴顯示子回覆

function showChildren($parent_id, $depth = 0) {
    global $conn;
    $sql = "SELECT * FROM bbsrow WHERE bbsrow_parentid = " . intval($parent_id) . " ORDER BY bbsrow_posttime";
    $result = mysql_query($sql, $conn);
    
    if (mysql_num_rows($result) == 0) return;
    
    echo "
";
    while ($row = mysql_fetch_assoc($result)) {
        echo "
";
        // 縮排視覺化
        echo str_repeat("  ", $depth);
        echo "{$row['bbsrow_title']} by {$row['bbsrow_auth']} ";
        echo "({$row['bbsrow_posttime']})
";
        echo nl2br(htmlspecialchars($row['bbsrow_content']));
        
        // 遞迴顯示子回覆
        if ($row['bbsrow_returncount'] > 0) {
            showChildren($row['bbsrow_id'], $depth + 1);
        }
        echo "
";
    }
    echo "
";
}

主程式流程

<?php
$conn = mysql_connect("localhost", "user", "pass") or die("連線失敗");
mysql_select_db("forum", $conn) or die("選庫失敗");
mysql_query("SET NAMES utf8");

// 1. 取得所有主題文 (親文章)
$sql = "SELECT * FROM bbsrow WHERE bbsrow_parentid IS NULL ORDER BY bbsrow_posttime DESC";
$mainResult = mysql_query($sql, $conn);

// 2. 逐筆顯示主題文及其回覆樹
while ($main = mysql_fetch_assoc($mainResult)) {
    echo "
";
    echo "
{$main['bbsrow_title']}
";
    echo "
作者: {$main['bbsrow_auth']} | 時間: {$main['bbsrow_posttime']}
";
    echo "
" . nl2br(htmlspecialchars($main['bbsrow_content'])) . "
";
    
    // 顯示回覆樹
    if ($main['bbsrow_returncount'] > 0) {
        showChildren($main['bbsrow_id']);
    }
    echo "
";
}

// 3. 分頁邏輯 (簡易版)
$perPage = 10;
$page = isset($_GET['page']) ? max(1, intval($_GET['page'])) : 1;
$offset = ($page - 1) * $perPage;
// ... 修改主題文查詢加 LIMIT $offset, $perPage
// ... 計算總頁數輸出分頁連結
?>

效能優化與改進方向

現代化重構範例 (mysqli + 單查詢建樹)

$sql = "SELECT * FROM bbsrow WHERE bbsrow_parentid IS NULL ORDER BY bbsrow_posttime DESC LIMIT ?, ?";
$stmt = $mysqli->prepare($sql);
$stmt->bind_param("ii", $offset, $perPage);
$stmt->execute();
$threads = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);

// 一次撈取所有回覆
$allReplies = $mysqli->query("SELECT * FROM bbsrow WHERE bbsrow_parentid IS NOT NULL ORDER BY bbsrow_parentid, bbsrow_posttime")
                     ->fetch_all(MYSQLI_ASSOC);

// PHP 端建樹
$children = [];
foreach ($allReplies as $r) $children[$r['bbsrow_parentid']][] = $r;

function renderTree($parentId, $depth, $children) {
    if (!isset($children[$parentId])) return;
    echo "
";
    foreach ($children[$parentId] as $r) {
        echo "
" . str_repeat("→", $depth) . htmlspecialchars($r['bbsrow_title']) . "...";
        renderTree($r['bbsrow_id'], $depth+1, $children);
        echo "
";
    }
    echo "
";
}

foreach ($threads as $t) {
    echo "
" . htmlspecialchars($t['bbsrow_title']) . "
";
    renderTree($t['bbsrow_id'], 0, $children);
}