set default value in Zend select element

Question

I need to update forms on some site written not by me. It works on WordPress 4.3.1 with plugin WP-ZFF Zend Framework Full 1.11.12-1 installed so WP can use Zend classes.

There is a form what I need to check. The code:

class Form_Registration extends Zend_Form {

    public function init()
    {
        $this->setMethod(Zend_Form::METHOD_POST);
        $this->setEnctype(Zend_Form::ENCTYPE_URLENCODED);
        $this->setAction("/");
        $this->setAttrib("id", "registration_form");
        $this->setDecorators(array('FormElements', 'tag' => 'form'));

        $myselect = $this->createElement("select", "myselect");
        $myselect->addMultiOption("1","aa");
        $myselect->addMultiOption("2","bb");
        $myselect->addMultiOption("3","cc");
        $myselect->setValue("2");

        echo "value:".$myselect->getValue(); // that prints out "2"

        $this->addElements(array($myselect));
    }
}

and using of the code:

$f = new Form_Registration();
$f->isValid($_POST);
print $f->render(new Zend_View());

My problem is to set default value for this select element.

I've tried:

• $myselect->setValue("2");
• $this->setDefault('myselect','2');
• $this->populate(array('myselect' => '2'));

Also I've tried to replace $this->createElement() with $this->addElement() and so to replace it with

$this->addElement('select', 'myselect', array(
    'value' => '2',
    'multiOptions' => array(
            '1' => 'aa',
            '2' => 'bb',
            '3' => 'cc'
        ),
    )
);

I've disabled all Javascript to be sure that some script clears form elements. Nothing works! That what I get:

<select id="myselect" name="myselect">
<option value="1">aa</option>
<option value="2">bb</option>
<option value="3">cc</option>
</select>

What I do wrong and how can I set one of select's option to be 'selected'?