MYSQL插入多行

Question

我在我的PHP项目中使用MYSQL并且使用以下查询我有一个“奇怪的”（不确定我是无知的还是什么）：

public function vote($user) {

    $this->DB->prepare('INSERT INTO Ratings (Entry_ID, Rating, User) VALUES (:entry_id, :rating, :user);');
    $this->DB->bind(':entry_id', $this->getID(), \PDO::PARAM_INT);
    $this->DB->bind(':rating', 1, \PDO::PARAM_INT);
    $this->DB->bind(':user', $user);
    $this->DB->execute();
    $this->votes++;
}

进入下表：

// Ratings table
$DB->prepare("CREATE TABLE IF NOT EXISTS Ratings ("
            ."  Entry_ID int(11),"
            ."  ID int(11) AUTO_INCREMENT,"
            ."  Rating int(11),"
            ."  User varchar(255),"
            ."  PRIMARY KEY (ID),"
            ."  FOREIGN KEY (User) REFERENCES Users(Username)"
            ."  ON DELETE SET NULL ON UPDATE CASCADE,"
            ."  FOREIGN KEY (Entry_ID) REFERENCES Entries(Entry_ID)"
            ."  ON DELETE SET NULL ON UPDATE CASCADE"
            .") CHARACTER SET utf8;");
$DB->execute();

上一张表用于存储用户投的每一票。

问题是，每次执行第一个查询（INSERT）时，Ratings表中都会创建多个行。

编辑：在ajax响应脚本中调用vote函数：

session_start();

$entry = new Entry();

switch(filter_var($_POST["action"])){

    // Create Entry
    case "create":
        break;

    // Delete entry
    case "delete":
        break;

    // Rate entry
    case "rate":

        $entry->load($entry->decryptID(filter_var($_POST["entryId"])));
        $validator = new Validator();

        if($validator->checkRating(filter_var($_POST["rating"]), $entry->getEncryptedID(), filter_var($_SESSION["User"]))) {

            $entry->vote($_SESSION['User']);
            die();
            $entry->save();

            echo "OK";
        } else {

            echo "ERROR";
        }
        break;

    default: 

        echo "ERROR";
        break;   
}