PHP 实现知识问答网站中的推荐系统和个性化推荐功能。

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

// 获取用户ID
$userId = $_SESSION['userId'];

// 获取用户浏览记录
$questionId = $_GET['questionId'];
$answerId = $_GET['answerId'];

// 插入用户行为记录
$sql = "INSERT INTO user_behavior (user_id, question_id, answer_id, action_time) VALUES ('$userId', '$questionId', '$answerId', NOW())";
mysqli_query($conn, $sql);

// 计算用户的兴趣模型
function calculateUserInterest($userId) {
    // 连接数据库
    $conn = mysqli_connect('localhost', 'username', 'password', 'database');
    
    // 查询用户的浏览记录
    $sql = "SELECT question_id, answer_id FROM user_behavior WHERE user_id = '$userId'";
    $result = mysqli_query($conn, $sql);
    
    // 统计用户对每个问题的浏览次数
    $interestModel = array();
    while ($row = mysqli_fetch_assoc($result)) {
        $questionId = $row['question_id'];
        if (!isset($interestModel[$questionId])) {
            $interestModel[$questionId] = 0;
        }
        $interestModel[$questionId]++;
    }
    
    // 返回用户的兴趣模型
    return $interestModel;
}

// 示例调用
$userId = $_SESSION['userId'];
$interestModel = calculateUserInterest($userId);

// 根据用户的兴趣模型进行推荐
function recommendQuestions($interestModel) {
    // 连接数据库
    $conn = mysqli_connect('localhost', 'username', 'password', 'database');
    
    // 构建推荐查询语句
    $sql = "SELECT question_id, COUNT(*) AS score FROM user_behavior WHERE ";
    $conditions = array();
    foreach ($interestModel as $questionId => $interest) {
        $conditions[] = "question_id != '$questionId' AND (answer_id = '' OR answer_id NOT IN (SELECT answer_id FROM user_behavior WHERE user_id = '$userId' AND question_id = '$questionId'))";
    }
    $sql .= implode(" AND ", $conditions);
    $sql .= " GROUP BY question_id ORDER BY score DESC LIMIT 5";
    $result = mysqli_query($conn, $sql);
    
    // 返回推荐问题列表
    $recommendedQuestions = array();
    while ($row = mysqli_fetch_assoc($result)) {
        $recommendedQuestions[] = $row['question_id'];
    }
    
    // 返回推荐问题列表
    return $recommendedQuestions;
}

// 示例调用
$recommendedQuestions = recommendQuestions($interestModel);