custom form validation going wrong in codeigniter - codeigniter

Question

My custom function is not working. I am checking if passed value does not exist in the database it return error message. What I am doing wrong?
Controller function
function sp_exists($str)
{
$this->user_model->sp_exists($str);
$this->form_validation->set_message('sp_exists', 'The %s field does not exists');
}
Model function
function sp_exists($str)
{
$this->db->where('member_id',$str);
$query = $this->db->get('user');
if ($query->num_rows() > 0)
{
return false;
}
else
{
return true;
}
}
callback function
$this->form_validation->set_rules('sponsor_id', 'Sponsor ID', 'trim|required|xss_clean|callback_sp_exists');

Answer 1

Did you look at the user guide? It explains clearly how to do this.
First of all I think you should change the model function to this:
function sp_exists($str)
{
$this->db->where('member_id',$str);
$query = $this->db->get('user');
return $query->num_rows() > 0;
}
And the controller should look like this:
function sp_exists($str)
{
if(!$this->user_model->sp_exists($str))
{
$this->form_validation->set_message('sp_exists', 'The %s field does not exists');
return FALSE;
}
else
{
return TRUE;
}
}

Answer 2

change
function sp_exists($str)
{
$this->user_model->sp_exists($str);
$this->form_validation->set_message('sp_exists', 'The %s field does not exists');
}
to
function sp_exists($str)
{
$this->form_validation->set_message('sp_exists', 'The %s field does not exists');
return $this->user_model->sp_exists($str);
}