public function addToGroup($groupName, $elementName = '')
    {

		if(isset($this->groups[$groupName])){
			if(isset($this->groups[$groupName]['elements'])){
				if(!in_array($elementName, $this->groups[$groupName]['elements'])){
					$this->groups[$groupName]['elements'][] = $elementName;
				}
			}
		}

    }