function SignUpForm() {
return new Form($this, "SignUpForm", new FieldSet(
new EmailField("Email", "Email Address")

), new FieldSet(
new FormAction("signup", "Sign up")

), new RequiredFields(
         "Email"
));
}
function signup($data, $form) {
$member = new Member();
$form->saveInto($member);

$member->write();

if($group = DataObject::get_one('Group', "Code = 'ISA-NEWSLETTERS'")) {
$member->Groups()->add($group);
}

Director::redirect('thanks-for-registering/');
}