Zend Framework 2 formInput or formElement ID tag not rendering - forms

Question

In Zend framework 2, when I use the view's formRow method like so
$this->formRow($form->get('product_name'));
it will generate HTML like this
<label for="product_name">
<span>Name</span>
<input type="text" id="product_name" name="product_name">
</label>
but if I use formInput
<div class="control-group">
<?php echo $this->formLabel($form->get('product_name')->setLabelAttributes(array('class'=>'control-label'))); ?>
<div class="controls">
<?php echo $this->formInput($form->get('product_name')); ?>
</div>
</div>
$this->formInput($form->get('product_name'));
i don't get the id tag
<input type="" name="product_name">
I've tried with formElement with same results.
How can I get it to render just the input with all attributes and values?
This is how my Zend Framework 2 View looks like (simplified)
<?php echo $this->form()->openTag($form); ?>
<div class="control-group">
<?php echo $this->formLabel($form->get('product_name')->setLabelAttributes(array('class'=>'control-label'))); ?>
<div class="controls"><?php echo $this->formInput($form->get('product_name')); ?></div>
</div>
<div class="control-group">
<div class="controls"><?php echo $this->formSubmit($form->get('submit')); ?></div>
</div>
<?php echo $this->form()->closeTag(); ?>
and the Zend Framework 2 Form
<?php
namespace Product\Form;
use Zend\Form\Form;
class ProductForm extends Form
{
public function __construct($name = null)
{
// we want to ignore the name passed
parent::__construct('product');
$this->setAttribute('method', 'post');
$this->setAttribute('class','form-horizontal');
$this->add(array(
'name' => 'product_name',
'attributes' => array(
'type' => 'text',
),
'options' => array(
'label' => 'Name',
),
));
$this->add(array(
'name' => 'submit',
'attributes' => array(
'type' => 'submit',
'value' => 'Save',
'id' => 'submitbutton',
'class'=>'btn btn-success btn-large'
),
));
}
}
?>

Answer 1

Change:
$this->add(array(
'name' => 'product_name',
'attributes' => array(
'type' => 'text',
),
'options' => array(
'label' => 'Name',
),
));
to:
$this->add(array(
'name' => 'product_name',
'attributes' => array(
'type' => 'text',
'id' => 'product_name',
),
'options' => array(
'label' => 'Name',
),
));

Answer 2

Actually this code:
$this->add(array(
'type' => 'Zend\Form\Element\Text',
'name' => 'product_name',
'attributes' => array(
'id' => 'product_name',
'class' => 'span3',
),
'options' => array(
'label' => 'Your label',
),
));
could be used correctly by a css renderer like Bootstrap due to fact that the $this->formRow(...) form helper will produce:
<label for="product_name">Your label</label><input type="text" name="product_name" class="span3" id="product_name" value="">
which is more readable than the original formRow output (without id neither class attributes)