public function get_drug_names()
 {
     //for ajax
     $district = $_POST['category_id'];
     $facilities = Drug::get_drug_name_by_category($district);
     $list = "";
     foreach ($facilities as $facilities) {
         $list .= $facilities->Kemsa_Code;
         $list .= "*";
         $list .= $facilities->Drug_Name;
         $list .= "_";
     }
     echo $list;
 }