You can set formoptions rowpos and colpos in column property to define multiple column form layout  http://phpgrid.com/documentation/set_col_property/

Quick example:

$dg -> set_col_property("orderNumber", array("formoptions"=>array("rowpos"=>1,"colpos"=>1)));

Note that you may also need to increase the form width using set_form_dimension().

screenshot of 2-column layout example: 

http://screencast.com/t/Cm2itFlHkn1y