php - codeigniter callback from private methods not working -

i doing form validation in codeigniter using form validation library , custom callbacks.

public function insert_user() {     if($this->input->post('submit')) {         // load form validation library         $this->load->library('form_validation');          // configurations         $config = array(             array(                 'field' => 'username',                 'label' => 'username',                 'rules' => 'required|callback_username_check'             )         );         $this->form_validation->set_rules($config);          // .... continue ....     }    } 

when method public, working expected.

public function username_check($username) {     // stuffs here } 

when make method private, not working.

private function username_check($username) {     // stuffs here } 

why callbacks private methods not working?

why need this?

public methods in codeigniter controllers accessible urls example above

http://example.com/controller_name/username_check/blabla

i don't want callback methods accessible publicly.

the callback function must public. codeigniter form validation class access function @ current controller may not private..

to go around problem may think extending ci_form_validation class my_form_validation..

class my_form_validation extends ci_form_validation {     public function __construct()     {        parent::__construct();     }      function username_check($str)     {       /* code */     }  }  

then in validation must set only..

            'rules' => 'required|username_check'