CodeIgniter - Can not run $this->input->post(‘inputName’); in Modular Extensions - php

Question

As my title, I tried call that method but I got an error:
Fatal error: Call to a member function post() on a non-object in C:\xampp\htdocs\cifirst\application\modules\front\controllers\shopping.php on line 11
If I create a controller not in module, that method I can use very easy but in this case can not (everything code in method below can not run). This is my code:
public function add_to_cart() {
$data = array(
'id' => $this->input->post('productId'), // line 11
'name' => $this->input->post('productName'),
'price' => $this->input->post('productPrice'),
'qty' => 1,
'options' => array('img' => $this->input->post('productImg'))
);
$this->load->library('MY_Cart');
$this->cart->insert($data);
//redirect($_SERVER['HTTP_REFERER']);
//echo $_POST['productId'].'-'.$_POST['productName'];
}
And this code doesn't work too:
public function __construct() {
$this->load->library('cart');
$this->load->helper('form');
}
I'm using XAMPP 1.8.1, CodeIgniter 2.1.3 and newest MX. Please help me!

Answer 1

When you're using CodeIgniter functions outside of controllers, models, and views you need to get an instance of Codeigniter first.
class MyClass {
private $CI;
function __construct() {
$this->CI =& get_instance();
$this->CI->load->library('cart');
$this->CI->load->helper('form');
}
public function someFunction() {
$var = $this->CI->input->post("someField");
}
}

Answer 2

If you are calling:
$this->input->post('productId');
inside controller than the problem is with your constructor declaration or your class name
Your construct part should contain code like this:
Class Home extends CI_Controller
{
function __construct()
{
parent::__construct();
$this->CI->load->library('cart');
$this->CI->load->helper('form');
}
public function add_to_cart()
{
$data = array(
'id' => $this->input->post('productId'), // line 11
'name' => $this->input->post('productName'),
'price' => $this->input->post('productPrice'),
'qty' => 1,
'options' => array('img' => $this->input->post('productImg'))
);
}
}
It will work fine if you are calling from helpers function or any other classes than you should do something like this:
function __construct()
{
parent::__construct();
$this->CI->load->library('cart');
$this->CI->load->helper('form');
$this->CI =& get_instance();
}
public function add_to_cart()
{
$data = array(
'id' => $this->CI->input->post('productId'), // line 11
'name' => $this->CI->input->post('productName'),
'price' => $this->CI->input->post('productPrice'),
'qty' => 1,
'options' => array('img' => $this->CI->input->post('productImg'))
);
}