CI_Form_validation::integer PHP Method

    public function integer($str)
    {
        return (bool) preg_match('/^[\\-+]?[0-9]+$/', $str);
    }

 public function money($str)
 {
     //First check if decimal
     if (!parent::decimal($str)) {
         //Now check if integer
         return (bool) parent::integer($str);
     }
     return TRUE;
 }