二手回收网站利用PHP开发的优质用户评价系统

CREATE TABLE users (
   id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
   username VARCHAR(30) NOT NULL,
   email VARCHAR(50) NOT NULL,
   password VARCHAR(30) NOT NULL
);

CREATE TABLE feedback (
   id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
   user_id INT(6) UNSIGNED,
   comment VARCHAR(255) NOT NULL,
   rating INT(1) NOT NULL,
   FOREIGN KEY (user_id) REFERENCES users(id)
);

class FeedbackSystem {
   private $db;

   public function __construct($db) {
      $this->db = $db;
   }

   public function addFeedback($user_id, $comment, $rating) {
      $sql = "INSERT INTO feedback (user_id, comment, rating) VALUES ($user_id, '$comment', $rating)";
      $result = $this->db->query($sql);
      return $result;
   }

   public function getFeedbacks($user_id) {
      $sql = "SELECT * FROM feedback WHERE user_id = $user_id";
      $result = $this->db->query($sql);
      return $result->fetch_all(MYSQLI_ASSOC);
   }

   public function calculateAverageRating($user_id) {
      $sql = "SELECT AVG(rating) AS average_rating FROM feedback WHERE user_id = $user_id";
      $result = $this->db->query($sql);
      return $result->fetch_assoc()['average_rating'];
   }
}

// 用户发表评价
$feedbackSystem = new FeedbackSystem($db);
$feedbackSystem->addFeedback($user_id, $comment, $rating);

// 获取用户评价
$feedbacks = $feedbackSystem->getFeedbacks($user_id);
foreach ($feedbacks as $feedback) {
   echo $feedback['comment'];
   echo $feedback['rating'];
}

// 计算平均评分
$averageRating = $feedbackSystem->calculateAverageRating($user_id);
echo "平均评分：" . $averageRating;