$ _post问题，不知道变量

I want to check what is the problem with my $_post['name'] so I wanna check it what is in it, but it says this variable is not define. This problem is a simplified of this one.

messageform_view:

<div id="content">
<?php $this->load->helper('form'); ?>
<?php echo form_open("HomeController/insert_message"); ?>
    <p>
        <label for="name">Name: </label>
        <input type="text" name="name" id="name" value="" size="30" />
    </p>
    <p>
    <input type="submit" value="Submit" />
    </p>
<?php echo form_close(); ?>
</div>

message_model.php:

<?php 

class Message_model extends CI_Model {
    public function add_message()
    {

    }
}
?>

HomeController:

<?php

class HomeController extends CI_Controller
{
    public function index () {     
    } 
     public function insert_message()
    {           
        print_r($_POST['name']);
     }
}
?>

The Error:

A PHP Error was encountered

Severity: Notice

Message: Undefined index: name

Filename: controllers/HomeController.php

Line Number: 22

remove the below code from the view

<?php $this->load->helper('form'); ?>

in application/config/autoload.php add below code

$autoload['helper'] = array('form');

in controller to check value of form

print_r($this->input->post());die;

use this in view part : you will get the answer

<form action="<?php echo base_url('HomeController/insert_message'); ?>" method="post">
    <p>
     <label for="name">Name: </label>
    <input type="text" name="name" id="name" value="" size="30" />
    </p>
    <p>
     <input type="submit" value="Submit" />
    </p>
    </form>

in controller get the name field as

$name = $this->input->post('name');

</div>