Zend Framework validation: set element value to empty string when there is no data in POST - forms

Question

I'm sorry if my question is a bit dumb, but I have looked at other questions/Googled this and still didn't get it.
I have a form with default and custom elements:
class Form_Client extends Planner_Form {
public function init() {
$this->addPrefixPath('Planner_Form_Element', 'Planner/Form/Element', 'element');
$this->setAttrib('name', 'clientForm');
$this->addElement('text', 'phone', array(
'label' => 'Телефон',
'required' => true,
'filters' => array('Digits'),
'ng-model' => 'clientForm.phone',
));
$this->addElement('text', 'extra_phone_1', array(
'label' => 'Дополнительный телефон',
'required' => false,
'filters' => array(
array('Digits'),
),
'ng-model' => 'clientForm.extra_phone_1',
));
$this->addElement('text', 'name', array(
'label' => 'Имя',
'required' => false,
'ng-model' => 'clientForm.name',
));
$this->addElement('datetime', 'birthday', array(
'label' => 'Дата рождения',
'required' => false,
'ng-model' => 'clientForm.birthday',
));
I send form via AngularJs, and when I check it
if ($request->isPost()) {
$body = $this->getRequest()->getRawBody();
$data = Zend_Json::decode($body);
Zend_Debug::dump($data);
$form = new Form_Client();
if ($form->isValid($data)) {
$values = $form->getValues();
Zend_Debug::dump($values);
}
I get the following:
array(1) {
["phone"] => string(10) "9138521376"
}
array(4) {
["phone"] => string(10) "9138521376"
["extra_phone_1"] => string(0) ""
["name"] => NULL
["birthday"] => NULL
}
So my question is: why extra_phone_1 field gets empty string, and name gets NULL? Is it because of filter on extra_phone_1 field? If so, how can I set field value to empty string, when there is no data in POST for this field?

Answer 1

You are right, the value is'' due Digits filter and null without this filter.
To have a non-null value in the name field, for example, you can use the same technique and try to put the filter 'StringTrim'