src/model/UserDbLdap.php
public static function getAdldapProvider() {
        if(static::getExtensionOptions('adldap-providername') != '__USE_DEFAULT_PROVIDER__') {
            $provider = Yii::$app->ad->getProvider(static::getExtensionOptions('adldap-providername'));
        } else {
            $provider = Yii::$app->ad->getDefaultProvider();
        }

        return $provider;        
    }
public static function getAdldapProvider() {
        if(static::getExtensionOptions('adldap-providername') != '__USE_DEFAULT_PROVIDER__') {
            $provider = Yii::$app->ad->getProvider(static::getExtensionOptions('adldap-providername'));
        } else {
            $provider = Yii::$app->ad->getDefaultProvider();
        }

        return $provider;        
    }
Get the Adldap2 provider name from the extension options.
See constant variable EXTENSION_OPTIONS_DEFAULT at the top of the class