SPIP 1.9 If we create a form which has its operational action as a link that takes arguments (for example, when you use the #SELF tag with the default type of URL), then we must submit those values in hidden fields; this function evaluates the form and calculates the fields in question in such a case. It is used as shown in the example below:
<form action="#SELF">
[(#SELF|form_hidden)]
...
</form>