13. 论坛系统CMS

代码：

// db.php - 数据库连接
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "forum_system_cms";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// create_topic.php - 创建新话题
if(isset($_POST['create_topic'])){
    $title = $_POST['title'];
    $content = $_POST['content'];
    $category = $_POST['category'];
    $author = $_POST['author'];
    
    $sql = "INSERT INTO topics (title, content, category, author) VALUES ('$title', '$content', '$category', '$author')";
    if(mysqli_query($conn, $sql)){
        echo "Topic created successfully!";
    } else {
        echo "Error: " . $sql . "<br>" . mysqli_error($conn);
    }
}

// show_topics.php - 显示所有话题
$query = "SELECT * FROM topics ORDER BY created_at DESC";
$result = mysqli_query($conn, $query);
while($row = mysqli_fetch_assoc($result)) {
    echo "<h2>" . $row['title'] . "</h2>";
    echo "<p>" . $row['content'] . "</p>";
    echo "<p>Category: " . $row['category'] . "</p>";
    echo "<p>Author: " . $row['author'] . "</p>";
}

// add_reply.php - 添加回复
if(isset($_POST['add_reply'])){
    $topic_id = $_POST['topic_id'];
    $reply = $_POST['reply'];
    
    $sql = "INSERT INTO replies (topic_id, reply) VALUES ('$topic_id', '$reply')";
    if(mysqli_query($conn, $sql)){
        echo "Reply added!";
    } else {
        echo "Error: " . $sql . "<br>" . mysqli_error($conn);
    }
}

// show_replies.php - 显示回复
$topic_id = $_GET['topic_id'];
$query = "SELECT * FROM replies WHERE topic_id = '$topic_id'";
$result = mysqli_query($conn, $query);
while($row = mysqli_fetch_assoc($result)) {
    echo "<p>" . $row['reply'] . "</p>";
}