White screen of death in hook form alter

Question

I have enabled simplenews module in drupal 8 and I am trying to reduce the width of input field from 60 to 30. I am trying to implement form alter hook and have devel module installed. I used dsm($form_id); to identify form and then in order to identify the form attribute to change, I tried to use dsm($form), dpm($form) and print_r($form) and all these are giving white screen of death.

function custom_newsletter_form_alter(&$form,  $form_state, $form_id) {  
  if ($form_id == 'simplenews_subscriptions_block_2138c21c-6453-4b7d-92d6-9407e427a78a') {
    dsm($form); 
    dpm($form); 
    print_r($form);
  }  
}

I have tried different drupal 8 installations both localhosted and web hosted, tried with different themes but I am not able to print form. Is there any other way to identify/target correct form attribute to change like DOM inspecter of firebug?

Answer 1

It seems that dsm() and dpm() are not supported in Drupal 8. They are replaced by kint(). I have enabled the devel kint sub-module and used kint($form) to print my form array. You can also use ksm($form).

Answer 2

You can use \dpm($form) as per OOP because devel is in a different namespace.