ZF2占位符不会出现在html代码中

I am trying to make a simple login form. The username element

    $this->add(array(
        'name' => 'username',
        'type' => 'Text',
        'options' => array(
            'label' => 'Username',
            'placeholder' => 'user@domain.com'
        ),
    ));

The placeholder does not appear in the created form. Note that the 'label' appears correctly...

If I set it in controller code, it appears

$form->get('username')->setAttribute('placeholder',"user@domain.com");

Same problem for the button, I have to set

$form->get('submit')->setValue('Signin');

otherwise it just shows 'Add' for some reason...

Any ideas on what may be the problem?

Nevermind, newbie mistake. The placeholder should be in attributes apparently.

    $this->add(array(
        'name' => 'username',
        'type' => 'Email',
        'options' => array(
            'label' => 'Username: ',
        ),
        'attributes' => array(
            'placeholder' => 'user@domain.com',
        )
    ));

Problem of blindly following a blog post at -> http://programming-tips.in/zend-framework-2-login-with-zend-auth