code: function dropdown()
      {
          $args = func_get_args();
  
          if(count($args) == 2)
          {
              list($key, $value) = $args;
          }
          else
          {
              $key = $this->primary_key;
              $value = $args[0];
          }
  
          $this->trigger('before_dropdown', array( $key, $value ));
  
          $this->apply_soft_delete_filter();
  
          $result = $this->_database->select(array($key, $value))
              ->get($this->_table)
              ->result();
  
          $options = array();
  
          foreach ($result as $row)
          {
              $options[$row->{$key}] = $row->{$value};
          }
  
          $options = $this->trigger('after_dropdown', $options);
  
          return $options;
      }
docs: Retrieve and generate a form_dropdown friendly array