The 3.8 code for Fabrik is now available on github, in the 'master' branch. If you are familiar with updating Fabrik from github, we would appreciate it if you could test this code on J! 3.8 for us. Once we have some feedback, we'll build a 3.8 release.
Element default examples
Many elements have both a "default" option and an "eval" option.
When you turn on "eval", the text entered in the "default" option is treated as PHP.
The PHP expression is evaluated and the data 'returned' is used as the element's default value.
return 'a string';
return FabrikHelperElement::filterValue(81); //81 is the id of the filter element
$myInput = JFactory::getApplication()->input;
$myParam = $myInput->get('urlparam','');