yii2 php namespace 引入第三方非namespace库文件时候，报错：Class not found 的解决

一个类文件时namespace的库方式

通过下面的方式引入类,报错  Class Not Found：

namespace frontend\block\customer\account;use Yii;use frontend\block\Blockbase;//use yii\base\Model;//use backend\models\helper\Base.phpuse frontend\models\core\Request;use frontend\models\core\Customer;use frontend\models\core\User;use frontend\models\core\Url;use frontend\models\core\Func;use frontend\models\core\Email;use frontend\models\core\Help;use frontend\models\core\Session;use frontend\models\core\Config;use frontend\models\core\Store;use frontend\models\core\Message;use frontend\models\core\Date;use frontend\models\core\Mongodb;use Facebook\FacebookSession;use Facebook\FacebookRedirectLoginHelper;use Facebook\FacebookRequest;use Facebook\FacebookResponse;use Facebook\FacebookSDKException;use Facebook\FacebookRequestException;use Facebook\FacebookAuthorizationException;use Facebook\GraphObject;use Facebook\Entities\AccessToken;use Facebook\HttpClients\FacebookCurlHttpClient;use Facebook\HttpClients\FacebookHttpable;class Login extends Blockbase{   public function getGoogleLoginUrl(){        $lib_google_base = Yii::getAlias("@common/lib/google");        //echo $lib_google_base.'/Social.php';exit;        $lib_google_base = Yii::getAlias("@common/lib/google");        include $lib_google_base.'/Social.php';        $Social_obj= new Social();        $url = $Social_obj->google();        return $url;    }}

需要把$Social_obj= new Social(); 改成：

$Social_obj= new \Social();

也就是加入一个反斜杠，哈哈，折腾了我1个小时。