Please Help Me, Call_back validation function not triggered

[eluser]vickatg[/eluser]
I do know this topic has been discussed alot, i went through almost all discussions regarding this topic yet i couldn’t solve my problem.
My case is that, i want to validate if the username a user wants to register already exists in the database, if it exists registration form should prompt back demanding a new username.
I did all i could to implement the scenario unfortunately my call_back function isn’t working.

This is what i did.

1. created MY_Form_validation file that extends the validation class in application/libraries

Code:

if (!defined('BASEPATH')) exit('No direct script access allowed');
class MY_Form_validation extends CI_Form_validation
{
function run($module = '', $group = '') {
(is_object($module)) AND $this->CI =& $module;
return parent::run($group);
}
}

2.created a controller as follows

Code:

class Syst_conf_controller extends CI_Controller {

    public function __construct() {
        parent::__construct();
        $this->load->model('syst_conf/syst_conf_model');
         $this->load->library('form_validation');
         $this->form_validation->set_error_delimiters('<div class="validation_error">', '</div>');
      
    }

public function user()
    {

    if($this->input->post('new_user'))
    {
     // field name, error message, validation rules
    $this->form_validation->set_rules('first_name', 'First Name', 'trim|required|xss_clean');
    $this->form_validation->set_rules('surname','Surname','trim|required|xss_clean');
    $this->form_validation->set_rules('phone_number','Phone Number','trim|required|numeric|xss_clean');
    $this->form_validation->set_rules('email_address','Email Address','trim|required|valid_email');
    $this->form_validation->set_rules('rank','Rank','trim|required|xss_clean');
    $this->form_validation->set_rules('username','Username','callback__username_check');
    $this->form_validation->set_rules('password','Password','trim|required|matches[cpassword]');
    $this->form_validation->set_rules('cpassword','Password Confirmation','trim|required');
              
        if ($this->form_validation->run($this) == FALSE)
         {
                    $content['contents'] = NULL;
                    $content['form_data'] =  $this->syst_conf_model->load_user_groups();
                    $this->load->view('syst_conf/new_user',$content);
         }
                 else
                 {
                 $query = $this->syst_conf_model->create_user();
                 if($query)
                 {
                 $content = array('contents' => 'user successfully added');
                 $this->load->view('syst_conf/new_user',$content);
                 }
                 else{
                 $content = array('contents' => 'an error occured while updating data');
                 $this->load->view('syst_conf/new_user',$content);
                 }
                 }
      
    }
    else
    {
      
        $content['contents'] = NULL;
        $content['form_data'] =  $this->syst_conf_model->load_user_groups();
    $this->load->view('syst_conf/new_user',$content);
    }
    }

      //this functions validates if the selected username exists in the database
       function _username_check()
       {
       $username= $this->input->post('username');
       $result = $this->syst_conf_model->check_username($username);
       if(strcasecmp($result, "TRUE")==0)
       {
       $this->form_validation->set_message('username_check', 'please choose another username, that one is already taken');
       return FALSE;
       }
       else
       {
       return TRUE;
       }
       }
}

3. below is my model

Code:

class Syst_conf_model extends CI_Model {

    function __construct() {
        parent::__construct();
    }

      function check_username($username)
       {
       $sql = "select username from tbl_user where username='$username'";
       $query = $this->db->query($sql);
       if($query->num_rows() == 0)
       {
        return FALSE;
       }
       else
       {
        return TRUE;
       }
       }

The question is, what should i do to trigger my call_back function?

[eluser]toopay[/eluser]
Its automatic trigered! but your function name is incorrect and your callback function should have an initial params!

Code:

//this functions validates if the selected username exists in the database
       function username_check($str)
       {
          //$username= $this->input->post('username');
          $result = $this->syst_conf_model->check_username($str);
          if( ! $result)
          {
             $this->form_validation->set_message('username_check', 'Something wrong at %s field!');
             return FALSE;
          }
          else
          {
             return TRUE;
          }
       }

[eluser]toopay[/eluser]
also, make sure you just use one '_' when you set the rules :

Code:

// Yours now :
$this->form_validation->set_rules('username','Username','callback__username_check');
// Should be
$this->form_validation->set_rules('username','Username','callback_username_check');

[eluser]vickatg[/eluser]
thanks alot! things are now on ma way