Zend Framework multiple form elements names - zend-framework

Question

I have multiple Zend Framework(v1.12) forms in my application.
Main form:
<?php
class Application_Form_Main extends Zend_Form
{
public function init()
{
$this->setMethod('post')->setAction('some/url');
}
}
?>
My subform:
<?php
class Application_Form_User extends Zend_Form_SubForm
{
public function init()
{
//first name element
$this->addElement('text',
'first_name',
array(
'label' => 'Name',
'required' => true,
'filters' => array('StringTrim')
)
);
//last name element
$this->addElement('text',
'last_name',
array(
'label' => 'Surname',
'required' => true,
'filters' => array('StringTrim')
)
);
$this->setElementDecorators(array(
'ViewHelper',
'Errors'
));
}
}
?>
In my custom controller (for example UsersController.php) Im rendering main form with multiple user subforms:
<?php
$mainForm = new Application_Form_Main();
for($i=0; $i<2; $i++){
$userForm = new Application_Form_User();
$mainForm->addSubForm($userForm, 'user_'.($i+1));
}
//passing main form to the template
$this->view->mainForm = $mainForm;
?>
So Im getting the form with 2 users first_name and last_name fields.
In my template Im rendering form this way:
<form action="<?php echo $this->mainForm->getAction(); ?>"
enctype="<?php echo $this->form->getEnctype(); ?>"
method="<?php echo $this->form->getMethod(); ?>"
">
<?php echo $this->mainForm->getSubForm('user_1')->first_name; ?>
<?php echo $this->mainForm->getSubForm('user_1')->last_name; ?>
<?php echo $this->echo $this->mainForm->getSubForm('user_2')->first_name; ?>
<?php echo $this->echo $this->mainForm->getSubForm('user_2')->last_name; ?>
</form>
The problem is first_name and last_name text field names are identical in both forms. How can I make it to have unique names? If I output the form:
<?php echo $this->mainForm; ?>
Then everything is ok, I get different field names.
So any ideas?