检测isset、empty、other时出现stdClass问题

首先让我说我正在使用CodeIgniter和Elliot Haughin创建的Facebook类。http://www.haughin.com/code/facebook/我有工作发现一切都很好。然而，当我用各种FB帐户测试我的代码时，我偶然发现了一个我想评估的问题，但我的尝试失败了。我在谷歌上搜索过其他论坛，一直都能找到我最初想到的答案。一些无论如何都应该有效但在这种情况下似乎无效的东西。。

既然我已经说过了，我的问题是。FB传递回的对象中并不总是有特定的条目。为了这个例子，我说用户名。。

以下是使用用户名返回的数据示例：

facebookResponse Object
(
    [__construct:private] => 
    [__resp] => stdClass Object
        (
            [data] => stdClass Object
                (
                    [id] => 0000000000000
                    [name] => Random.User
                    [first_name] => Random
                    [middle_name] => ...
                    [last_name] => User
                    [link] => http://www.facebook.com/profile.php?id=000000000
                    [birthday] => 11/26/1980
                    [gender] => male
                    [timezone] => -4
                    [locale] => en_US
                    [verified] => 1
                    [updated_time] => 2011-05-30T19:24:53+0000
                )

下面是一个没有用户名的例子：

facebookResponse Object
(
    [__construct:private] => 
    [__resp] => stdClass Object
        (
            [data] => stdClass Object
                (
                    [id] => 000000000000000000000
                    [name] => Random User
                    [first_name] => Random
                    [last_name] => User
                    [link] => http://www.facebook.com/Random.User
                    [username] => Random.User
                    [birthday] => 11/10/1985
                    [hometown] => stdClass Object
                        (
                            [id] => 000000000000000
                            [name] => Coventry, Connecticut
                        )
                    [location] => stdClass Object
                        (
                            [id] => 00000000000000
                            [name] => San Jose, California
                        )

我最后一次尝试解决问题失败了，大概是。。

        $fb_result = $this->facebook->call('get', 'me', array('metadata' => 1));
        $fbFirstName = $fb_result->first_name;
        $fbLastName = $fb_result->last_name;
        $fbUserName = $fb_result->username;
        $fbUserId = $fb_result->id;
        $fbHomeTown = $fb_result->hometown->name;
        $fbLocation = $fb_result->location->name;
        echo "<strong>First Name: </strong>"; if((isset($fbFirstName))AND(!empty($fbFirstName))AND(trim($fbFirstName) !== "")){echo $fb_result->first_name ."<br />"; }else{ echo "Not found.<br />"; }
        echo "<strong>Last Name: </strong>"; if((isset($fbLastName))AND(!empty($fbLastName))AND(trim($fbLastName) !== "")){echo $fb_result->last_name."<br />"; }else{ echo "Not found.<br />"; }
        echo "<strong>Username: </strong>"; if((isset($fbUserName))AND(!empty($fbUserName))AND(trim($fbUserName) !== "")){echo $fb_result->username."<br />"; }else{ echo "Not found.<br />"; }
        echo "<strong>User FB ID: </strong>"; if((isset($fbUserId))AND(!empty($fbUserId))AND(trim($fbUserId) !== "")){echo $fb_result->id."<br />"; }else{ echo "Not found.<br />"; }   
        echo "<strong>Location hometown: </strong>"; if((isset($fbHomeTown))AND(!empty($fbHomeTown))AND(trim($fbHomeTown) !== "")){echo $fb_result->hometown->name."<br />"; }else{ echo "Not found.<br />"; }
        echo "<strong>Location current (manual input): </strong>"; if((isset($fbLocation))AND(!empty($fbLocation))AND(trim($fbLocation) !== "")){echo $fb_result->location->name."<br />"; }else{ echo "Not found.<br />"; }

然而，在我首先将其定义为一个变量，然后用if else检查它的情况下进行操作是可行的。由于一个错误，我现在得到"正在尝试获取非对象的属性"。这意味着我想，由于它不存在，我正试图将它设置为一个变量，不管它会为它带来错误。我花了一天和昨天的大部分时间试图解决这个问题，我不得不说我被卡住了。php错误类型只不过是一个"通知"，但我通常不喜欢让我的代码处于这样的状态，即使是这样的错误也会卷土重来。。也就是说我迷路了。。