controllers/SettingsController.php
public function connect(ClientInterface $client)
    {
        $attributes = $client->getUserAttributes();
        $provider   = $client->getId();
        $clientId   = $attributes['id'];

        $account = $this->finder->findAccountByProviderAndClientId($provider, $clientId);

        if ($account === null) {
            $account = \Yii::createObject([
                'class'     => Account::className(),
                'provider'  => $provider,
                'client_id' => $clientId,
                'data'      => json_encode($attributes),
                'user_id'   => \Yii::$app->user->id,
            ]);
            $account->save(false);
            \Yii::$app->session->setFlash('success', \Yii::t('user', 'Your account has been connected'));
        } else if (null == $account->user) {
            $account->user_id = \Yii::$app->user->id;
            $account->save(false);
        } else {
            \Yii::$app->session->setFlash('error', \Yii::t('user', 'This account has already been connected to another user'));
        }

        $this->action->successUrl = Url::to(['/user/settings/networks']);
    }
public function connect(ClientInterface $client)
    {
        $attributes = $client->getUserAttributes();
        $provider   = $client->getId();
        $clientId   = $attributes['id'];

        $account = $this->finder->findAccountByProviderAndClientId($provider, $clientId);

        if ($account === null) {
            $account = \Yii::createObject([
                'class'     => Account::className(),
                'provider'  => $provider,
                'client_id' => $clientId,
                'data'      => json_encode($attributes),
                'user_id'   => \Yii::$app->user->id,
            ]);
            $account->save(false);
            \Yii::$app->session->setFlash('success', \Yii::t('user', 'Your account has been connected'));
        } else if (null == $account->user) {
            $account->user_id = \Yii::$app->user->id;
            $account->save(false);
        } else {
            \Yii::$app->session->setFlash('error', \Yii::t('user', 'This account has already been connected to another user'));
        }

        $this->action->successUrl = Url::to(['/user/settings/networks']);
    }
Connects social account to user.
@param  ClientInterface $client
@return \yii\web\Response