public function __construct(array $allowedTags = array(), array $allowedFilters = array(), array $allowedMethods = array(), array $allowedProperties = array())
 {
     parent::__construct($allowedTags, $allowedFilters, $allowedMethods, $allowedProperties);
     $this->allowedTags = array_merge($this->allowedTags, array('if', 'for'));
     $this->allowedFilters = array_merge($this->allowedFilters, array('date', 'encoding', 'default'));
 }