In the additem method for the KoolComboBox, you may add a data array to it.
Adding the check after checking if the data is set would eliminate errors generated in the loop if it were not an array.

function addItem($_text="",$_value="",$_data=array(),$_selected=false,$_enabled=true)
	{
		$_item = new KoolComboboxItem();
		$_item->enabled = (isset($_enabled))?$_enabled:false;
		$_item->selected = (isset($_selected))?$_selected:false;
		if($_text!="") $_item->data["text"] = $_text;
		$_item->data["value"] = $_value;
		if (isset($_data)&& is_array($_data) )  // check if $_data is an array Anthony
		{
			foreach($_data as $_k=>$_v)
			{
				$_item->data[$_k] = $_v;	
			}			
		}				
		array_push($this->_items,$_item);
		return $_item;
	}