code: public function resetAllPropertiesExcept($properties=array())
    {
      foreach ($this->obj_to_db_trans as $obj_prop => $db_field) {
        if(  !in_array($obj_prop,$this->key_properties) && !in_array($obj_prop,$properties) ){
          $this->{$obj_prop}=null;
        }
      }
    }
docs: Reset all properties except the keys and the given properties
  
  Usefull for when you want only to update a specific field in the
  database.
  
  @param array $properties