dhtmlxform - params names

why there is a ‘null_’ prefix in all of the params ?

Which use-case do you mean?
Please provide more details.

in editing mode, i want to log some info(values from form) but $this->_getParam("") returns null, $this->getParam("null") is working.
btw can you add feature to get id of inserted row ?

Do you mean dhtmlxform or grid-in-form integration?
In second case mask , which used by field names can be defined by setFieldName command
docs.dhtmlx.com/doku.php?id=dhtm … tfieldname