How to do a negative form validation in codeigniter?

Question

is_unique is the form validation which not allow the value exist in the database. But, can I do the opposite one? for example, I would like to need the value w

Answer 1

Try your own callback function

$this->form_validation->set_rules('email', 'Email', 'required|max_length[32]|valid_email|callback_email_check');

Function will be something like this

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