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

You can do it like this

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

Controller method

public function email_available($str)
{
    // You can access $_POST variable
    $this->load->model('mymodel');
    $result =   $this->mymodel->emailAvailability($_POST['email']);
    if ($result)
    {
        $this->form_validation->set_message('email_available', 'The %s already exists');
        return FALSE;
    }else{
        return TRUE;
    }
}

Model mymodel.php

public function emailAvailability($email)
{
    $this->db->where('email',$email);
    $query  =   $this->db->get('tablename');
    return $query->row();
}