Various other special parameters can be sent to the form when it is loaded to modify its original behaviour:
message_ok, message_erreur
The success message is generally supplied by the traiter function; the error message is supplied by the verifier or traiter functions. It is nonetheless possible to supply them using the charger function in exceptional circumstances.
action
This value specifies the URL to which the form is posted. By default, it is the same URL as the current page, which makes it possible to redisplay the form if errors are detected. For other very special use cases, this URL can be altered.
_forcer_request
When a form is submitted, SPIP identifies it so as to be able to have several forms of the same type on a single page, and to only process the one that has been submitted. This verification is based on the list of arguments passed to the #FORMULAIRE_XXX tag.
In some cases where these arguments change after data entry, SPIP can make a mistake and assume that the data comes from another form.
Sending _forcer_request as true indicates to SPIP that it should not perform this verification and ought to process the entry data in every circumstance.
_action
If the processing of the form must call a directory function actions/ protected by securiser_action(), it is useful to specify the name of the action so that SPIP automatically supplies the corresponding protection hash.
_hidden
The value of this field will be added directly to the HTML of the generated form. it is often used to add "hidden" type input fields which should be written out explicitly:
$valeurs['_hidden'] = "<input type='hidden' name='secret' value='shhhhh !' />";