Preprocess function trying to alter title

Question

I have used this code in template.php.

function mytemplate_preprocess_node(&$variables) {
  $variables['title'] = "trial" . check_plain($node->title);
}

I was trying to alter the page title, and wanted to make a test before. When I use that code, the title disappears from the teaser. Do you know why?

Answer 1

template_preprocess_node() uses the following code.

  $variables['node'] = $variables['elements']['#node'];
  $node = $variables['node'];

  $variables['date'] = format_date($node->created);
  $variables['name'] = theme('username', array('account' => $node));

  $uri = entity_uri('node', $node);
  $variables['node_url'] = url($uri['path'], $uri['options']);
  $variables['title'] = check_plain($node->title);

It is perfectly fine, to set $variables['title'] in hook_preprocess_node() instead of calling drupal_set_title()/drupal_get_title(). The error in the code shown by the OP is not setting the local $node variable. The correct code is the following one.

// Drupal 7
function mytemplate_preprocess_node(&$variables) {
  $variables['title'] = "trial" . check_plain($variables['node']->title);
}

In Drupal 8, the equivalent for the code I wrote would be the following one.

// Drupal 8
function mytemplate_preprocess_node(&$variables) {
  $variables['label'] = "trial" . check_plain($variables['node']->label());
}

This would not change the title used for the <title> though. If you need to change that as well, you should use the following code.

// Drupal 7
function mytemplate_preprocess_node(&$variables) {
  $variables['title'] = "trial" . check_plain($variables['node']->title);
  drupal_set_title("trial" . check_plain($variables['node']->title), PASS_THROUGH);
}

Answer 2

You shouldn't be using that to alter the page title, you can just use drupal_set_title();

Answer 3

Also inducing title to the $variables array will not change the page title in the browser tab. So as already suggested page title can be set conditionally as below.

function mytheme_preprocess_page(&$variables) {
  if(isset($variables['node']) && $variables['node']->type == "your_content_type") {
    drupal_set_title("my_title");    
  }
}

Answer 4

The title 'disappears' because you are assigning and undefined value to it. You're using $node, but that variable isn't in scope/defined.

Use:

$node = $variables['node'];
$variables['title'] = "trial" . check_plain($node->title);

Also, as Steven has already said, you should (ideally) use drupal_set_title() to set the page title. However, depending on when (in the page execution) you call this function, it may or may not affect the output of what you're seeing - it can be a bit tricky. It appears you're changing the title on the theme layer, at which point I'd say your approach is generally fine, but it may be nicer to do the change in something like template_preprocess_page(), instead.