From my testing it appears that the _form collection is not available in the On Request method in the Active4D.a4l file. I have tried to get values from the form variables using several methods but none seem to work from the On Request Method.
get request value
get form variables(array;array)
It does appear that the query params are available in the on request method just not the form values.
> From my testing it appears that the _form collection is not available in the On Request method in the Active4D.a4l file.
That's because it isn't meant to be available. The docs say:
"The handler is passed the path portion of the URL. The _query collection (or _form collection if “parameter mode” is set to “form variables” in Active4D.ini) is populated with the contents of the request’s query (if any), and is set to read-write mode so that you can directly modify the query."
If you want to change the URL based on a form variable, you'll need to do a redirect within a regular Active4D script.