zend framework2 - How to generate a new Csrf-Token for a Form -

i got form. when change select-element inside form, ajax-call same url, loads new form has additional fields or has fields removed (different categories, different fields...).

now, form request have same csrf-token, since token lives 1 request. meaning, have generate new token, whenever kind of action, have no idea on how this.

my assumption have like

if ($request->isxmlhttprequest()) {     $form->get('csrf')    ->regeneratecsrftoken() } 

but function doesn't exist, should alike lines. input appreciated

have tried this:

if ($request->isxmlhttprequest()) {     $form->get('csrf')->getcsrfvalidator()->gethash(true); } 

gethash(true) regenerate hash, , store changed hash in generator, form retrieve new value when retrieve element later.