TOPIC: Writing own plugin

public static function getUserGravatar($userId=null)
	{
			$default = self::noAvatar();
			if($userId == null)
			{
				$user = JFactory::getUser();
 
				if($user->guest){
					return $default;
				}
				$userId = $user->get('id');
			}
 
 
			$db = JFactory::getDbo();
			$query = $db->getQuery(true);
		        $query->select('image_folder, image_name');
		        $query->from('#__users_extended');
		        $query->where('user_id='.$db->quote($userId)); 
 
			$db->setQuery($query,0,1);			
			$r = $db->loadObject();
 
			if(empty($r)){
				return $default;
			}	
		        if(mb_strlen($r->image_folder)>0&&mb_strlen($r->image_name)>0){
			return '/images/hsu/'.$r->image_folder.'/'.$r->image_name;		
		        }else{
			return $default;
 
		      }
 
	}