Setting field attribute as read only in hook_form_alter?

Question

I'm trying to create a simple custom module to stop the Title of a specific node being edited.

function mymodule_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'nodetitle_node_form') {
    unset($form['title']);
  }
}

Currently it just removes any reference to the Title from the edit pages. Does anyone know how I can set the Title field attribute read only?

Answer 1

You can use the #disabled attribute:

function mymodule_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'nodetitle_node_form' && $form['nid']['#value']) {
    $form['title']['#disabled'] = TRUE;
  }
}

I made the assumption that you want this when editing nodes only (not when they are being added) which is what the && $form['nid']['#value'] part is for.