public function addColumn($id, $title, $options = array())
    {
        $returnValue = null;

        
		$replace = false;
		if(isset($options['replace'])){
			$replace = $options['replace'];
			unset($options['replace']);
		}
		if(!$replace && isset($this->columns[$id])){
			throw new common_Exception('the column with the id '.$id.' already exists');
		}else{
			$this->columns[$id] = new tao_helpers_grid_Column($id, $title, $options);
			//set order as well:
			$returnValue = true;
		}
        

        return $returnValue;
    }