How to fix a Num_row error

Why do you use a "third party" database class instead of the built-in database library CI is providing? See https://www.codeigniter.com/userguide3/d...index.html
Just set up the connection paramaters in application/config/database.php and you're good to go.
Start using the query builder right away. It will save you a lot of time and trouble.

Simple example (meant as a function in a model):

PHP Code:

Public function get_products($category=NULL)
{
   $this->db
   ->select('id,product_name,category,price')
   ->from('products');
   If ($category) {
     $this->db->where('category', $category);
  }
  $this->db->order_by('product_name','ASC' );
  $query = $this->db->get();
  If ($query->num_rows() > 0) {
     Return $query->result();
  }
  Else {
    Return FALSE;
  }
} 


This function will return an array of records (if there are any), or FALSE if there are no records found.