How to call database function into custom library in Codeigniter?

Question

I have created a library and am trying to access the database through it in codeigniter.

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class History {

function __construct() {
    //$CI->load->database();
    //$this->load->library('database');
    $CI =& get_instance();
    $CI->load->database();
}

public function create_history($id){
    //$this->load->database();
    $sql = "INSERT INTO inventory_history SELECT null,i.* FROM inventory i where i.inventory_id = :id";
    $query = $this->CI->db->conn_id->prepare($sql);
    $query->bindParam(':id', $id, PDO::PARAM_INT);
    return $query->execute();
}}

But I am getting error near the insert query. Going through Google I went around someone telling to use $this->ci->db to execute query. I'm not able to point out why there is error in database execution. How can I call database function into my custom library in codeigniter?

Answer 1

is it this?

class YourLibName {
   private $CI;

   function __construct() {
       $this->CI =& get_instance();
       $this->CI->load->database();
   }

}

Update: I think you should not load and use database object in library. You better create model and call it from library instead. A library should be independent and can be used with other application.