CodeIgniter: usign db inside My_Lang - php

Question

I found this useful Internationalization code:
http://pastebin.com/SyKmPYTX
everything works well except I am unable to connect to database.
what I need:
1) I need to check last segment
2) this is my db
DROP TABLE IF EXISTS `translate`;
DROP TABLE IF EXISTS `trans_data`;
DROP TABLE IF EXISTS `languages`;
/*Table structure for table `languages` */
CREATE TABLE `languages` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(50) NOT NULL,
`key` varchar(5) NOT NULL,
`default` tinyint(1) NOT NULL DEFAULT '0',
`display` tinyint(1) NOT NULL DEFAULT '0',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
/*Data for the table `languages` */
insert into `languages`(`name`,`key`,`default`,`display`) values
('GEO','ka',1,1),
('ENG','en',0,1),
('RUS','ru',0,1);
/*Table structure for table `trans_data` */
CREATE TABLE `trans_data` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(250) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
/*Table structure for table `translate` */
CREATE TABLE `translate` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`lang` int(11) NOT NULL,
`data` int(11) NOT NULL,
`trans` text NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `lang_2` (`lang`,`data`),
KEY `lang` (`lang`),
KEY `data` (`data`),
CONSTRAINT `translate_ibfk_1` FOREIGN KEY (`lang`) REFERENCES `languages` (`id`),
CONSTRAINT `translate_ibfk_2` FOREIGN KEY (`data`) REFERENCES `trans_data` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=340 DEFAULT CHARSET=utf8;
in the first I need to do something like this
$this->db->where('key', end($this->segments));
$query = $this->db->get('languages');
$lang = $query->row();
if(empty($lang)){
$this->db->where('default', 1);
$query2 = $this->db->get('languages');
$lang = $query2->row();
}
$lang_array = [
"lang_key" => $lang->key,
"lang_id" => $lang->id
];
$this->session->set_userdata($lang_array);
if(end($this->uri->segment_array()) == $lang->key){
unset($this->uri->segments[intval($this->uri->total_segments() - 1)]);
}
after this functionality
then I need to download translates from database and save it in object with this query
SELECT TD.`name` , T.`trans`
FROM `translate` AS T
INNER JOIN `languages` AS L ON (T.`lang` = L.`id`)
INNER JOIN `trans_data` AS TD ON (T.`data` = TD.`id`)
WHERE (L.`key` = :lang_key);
and when I call from view
echo $this->lang->line('trans_key');
I need to get the value
but I do not undestand how to edit this class to do this job...
can you help me and edit this class for me?
thank you for future...