Callback function ignoring other validation rules and executes first

On the HTML form, I have a field such as:

<?php
     $token = array(
       'name'          => 'pc_token',
       'id'            => 'pc_token',
       'class'         => 'form-control'           
       );
     echo form_input($token, set_value('pc_token')); ?>

The validation rules set on the field are:

$this->form_validation->set_rules(
    'pc_token', 'Token number', 'trim|required|min_length[5]|max_length[12]|callback_token_exists',
     array(
       'required'      =>  'You have not provided %s.',
       'token_exists'  =>  'The %s is not valid. Please recheck again'                 
       )
     );

And here is the function for the callback

public function token_exists($key)
{        
    $this->load->model('tokens');
    return $this->tokens->IsValidToken($key); // will return true if found in database or false if not found
}

The problem here is that when I keep the pc_token field empty/blank and submit the form, I don’t get the expected error message printed on screen.

Current Output

The Token number is not valid. Please recheck again

Expected Output

You have not provided Token number

So why does CI ignore the previous rules (such as required, min_length etc) in this case? If my assumption is correct, the direction is left to right and if even one fails, it does not move to the next rule.

Answer

try this in your callback function

check for empty

public function token_exists($key='')
{   

  if(empty($key)){
         $this->form_validation->set_message('token_exists', 'The {field} field is   required.');
         return FALSE;
   }else{
      $this->load->model('tokens');
      return $this->tokens->IsValidToken($key); 
    }

// will return true if found in database or false if not found
}