add class to fields on login block

Question

I am using drupal 7 and would like to customise my login form block.

function theme_form_alter(&$form, &$form_state, $form_id) {  

if ($form_id == "user_login_block") { $form['links'] = Null; // Remove Request New Password and other links from Block form //$form['links']['#markup'] = t('Forgotten Password?') . ' ' . t('Forgotten Password?') . ''; // Remove Request New Password from Block form //$form['links']['#markup'] = ' ' . t('Register') . '' . ' ' . t('Forgotten Password?') . ''; // Remove Request New Password from Block form

    $form['#prefix'] = '<div class="nano-ui">';
    $form['#suffix'] = '</div>';

    $form['name']['#attributes']['class'][]= array("nui-input");




    $form['name']['#title'] = Null; // Change text on form
    $form['name']['#attributes'] = array('placeholder' => t('username'));
    $form['pass']['#title'] = Null;
    $form['pass']['#attributes'] = array('placeholder' => t('password'));


}

}

In the above code the following line does not seem to have any effect on my field :

$form['name']['#attributes']['class'][]= array("nui-input");

Answer 1

This is what will work

    $form['#prefix'] = '<div class="nano-ui">';
    $form['#suffix'] = '</div>';

   $form['name']['#title'] = Null; // Change text on form
    $form['name']['#attributes'] = array('placeholder' => t('username'));
    $form['pass']['#title'] = Null;
    $form['pass']['#attributes'] = array('placeholder' => t('password'));

    $form['name']['#attributes']['class'][] = 'nui-input';

Here is the reference : How do I use hook_form_alter() to add CSS classes to a custom input field in user_register_form?