CI get_instance return null - codeigniter

Question

I using CI for my framework, and i don't know what is the error of this code
defined('BASEPATH') OR exit('No direct script access allowed');
class RajaOngkir extends CI_Controller {
private $api_key, $base_url;
public function __construct() {
// Pastikan bahwa PHP mendukung cURL
if (!$this->is_curl_exists()) {
log_message('error', 'cURL Class - PHP was not built with cURL enabled. Rebuild PHP with --with-curl to use cURL.');
}
$this->_ci=&get_instance();
var_dump($this->_ci);
$this->_ci->load->config('rajaongkir', TRUE);
// Pastikan Anda sudah memasukkan API Key di application/config/rajaongkir.php
if ($this->_ci->config->item('api_key', 'rajaongkir') == "") {
log_message("error", "Harap masukkan API KEY Anda di config.");
} else {
$this->api_key = $this->_ci->config->item('api_key', 'rajaongkir');
$this->base_url = $this->_ci->config->item('api_base_url', 'rajaongkir');
}
}
when i access it using web browser, its giving me error
Severity: Notice
Message: Trying to get property of non-object
Filename: controllers/rajaongkir.php
Line Number: 22
Fatal error: Call to a member function config() on a non-object in C:\xampp\htdocs\Koen_CI\application\controllers\rajaongkir.php on line 22
i think the error is when i call this->_ci=&get_instance. because its returning null value.
how to fix it?

Answer 1

You need to define the _ci variable in the class:
private $api_key, $base_url;
To
private $api_key, $base_url, $_ci;
But don't do that. As others mentioned in the comment, if you're in a controller, just use $this->something directly instead of $this->_ci. You should only use get_instance() when you're outside the CI structure (e.g. in a helper file).