下面是错误操作。php代码：

public function getUserByUserid($user_id){
    $stmt = $this->con->prepare("SELECT * FROM mydb.User WHERE user_id = ?" );
    $stmt->bind_param("s", $user_id);
    return $stmt->get_result()->fetch_assoc();
}

在另一个userlogin.php中，我在这里使用getuserbyuserid（$user\u id）：

if($db->userLogin($_POST['user_id'], $_POST['password'])){
    $user = $db->getUserByUserid($_POST['user_id']);
    $response['error'] = false;
    $response['user_id'] = $user['user_id'];
    $response['name'] = $user['name'];
    $response['contact_no'] = $user['contact_no'];
    $response['email'] = $user['email'];
    $response['role'] = $user['role'];

下面是错误信息：

<b>Fatal error</b>:  Call to a member function fetch_assoc() on a non-object in
<b>C:\xampp\htdocs\Android\includes\DbOperations.php</b> on line
<b>41</b>
<br />

第41行是： return $stmt->get_result()->fetch_assoc(); 不知道什么是fetch\u assoc（）问题，我是初学者…谢谢你的帮助：）