如何修复“Warning:mysqli_stmt::bind_param():类型定义字符串中的元素数与绑定变量数不匹配”[重复]

我正在为学校做这个项目,我遇到了这个问题,我想知道如何解决它,用户名在varchar中,密码也是,但部门在enum中

public function createUserAccount($username,$password,$department){
    if($this->userExists($username)){
        return "USER_ALREADY_EXISTS";
    }
    else{
        $pass_hash = password_hash($password,PASSWORD_BCRYPT,["cost"=>8]);
        $pre_stmt = $this->con->prepare("INSERT INTO `user`(`id`, `username`, `password`, `department`) VALUES (?,?,?,?)");
        $pre_stmt->bind_param("sss",$pass_hash,$username,$department);
        $result = $pre_stmt->execute() or die($this->con->error);
        if($result){
            return $this->con->insert_id;
        }
        else{
            return "some error";
        }
    }