public static function setLanguage($lang)
    {
        static::$_appLanguage = Yii::$app->language;

        Yii::$app->language = $lang;
    }
public static function setLanguage($lang)
    {
        static::$_appLanguage = Yii::$app->language;

        Yii::$app->language = $lang;
    }
public static function setLanguage ( $ lang ) { static :: $ _appLanguage = Yii :: $ app -> language ; Yii :: $ app -> language = $ lang ; }
Set new app language and save original language for future restore

@param string $lang
Set new app language and save original language for future restore