validation not working

[eluser]pickupman[/eluser]
Glad you got it working. Please note that the validation library has been deprecated 1.7.2 (removed in 2.0beta). You should form_validation library instead.

Also, it may be wise to set your username_check to a private method, as someone could visit that page right now. Or change your syntax to

Code:

$this->form_validation->set_rules('username', 'username', 'required|trim|callback__username_check');
$this->form_validation->set_rules('password', 'password', 'required|trim');
$this->form_validation->set_rules('passconf', 'password confirmation', 'required|trim|matches[password]');
$this->form_validation->set_rules('email', 'email address', 'required|trim|valid_email');

//Callback
function _username_check($str){
  if($str == 'test'){
     $this->form_validation->set_message('_username_check', 'The %s field can not be the word "test".');
     return FALSE;
  }
  return TRUE;
}

Also for those of us helping, using the code button in the editor will format your code so we can copy and paste it.