How add subcategory in Codeigniter - mysql

Question

i need add subcategory after category in this code:
Help pls
Controller:
public function find_diagnoz() {
$key = $this->input->get('key');
$result = $this->Diagnoz_model->find_diagnoz($key);
foreach ($result as $key => $res) {
/* Категория */
$this_cat = $this->Diagnoz_model->get_categories($res['id']);
if (!$this_cat) {
$rec->cat = false;
continue;
}
$result[$key]['cat'] = $this_cat['names'];
}
$html = '';
foreach ($result as $res) {
$html .= '<li>';
$html .= '<a href="javascript:void(0);" data-id="'.$res['id'].'" data-code="'.md5($res['id'].$res['texts']).'" data-title="'.$res['texts'].'" class="select_td">';
$html .= '<p>'.$res['texts'].'</p>';
$html .= '<p>Из категории: '.$res['cat'].'</p>';
$html .= '</a>';
$html .= '</li>';
}
die(json_encode(array('html' => $html)));
}
Model
For get category name:
public function get_category($id) {
$this_category = $this->db->select('*')
->from('zaloby')
->where('id = '.$id)
->get()->result_array();
if (!isset($this_category[0])) {
return false;
}
return $this_category[0];
}
For get result by key:
public function find_diagnoz($key) {
$res = $this->db->select('*')
->from('zaloby')
->like('names', $key)
->get()->result_array();
return $res;
}
Mysql table have structure:
id parid names text
1 0 name1 desc1
2 1 name2 desc2
3 2 name3 desc3
4 2 name4 desc4
When I search result now, my result:
Name2
In category: Name2
I need result with subcategory:
Name2
In category: Name1 / Name2
Thx, sorry for my bad english.