Hook to change page title - drupal

Question

I want to programmatically alter a page title in Drupal 8 so that it will be hard-coded in the theme file.
I'm attempting to use a hook function to preprocess_page_title, but it seems to not understand what page to change the title on.
Here's what I have so far:
function test_preprocess_page_title(&$variables) {
if (arg(0) == 'node/12') {
$variables['title'] = 'New Title';
}
}
I figured the only way to make this change on one specific page is to set the node argument. Has any one figured out a way to override page title on Drupal?

Answer 1

In your template.theme file add the preprocessor and then override page-title.html.twig in your template folder by printing the variable, like below:
function theme_preprocess_page_title(&$variables) {
$node = \Drupal::request()->attributes->get('node');
$nid = $node->id();
if($nid == '14') {
$variables['subtitle'] = 'Subheading';
}
}
then {{ subtitle }}

Answer 2

Here's the method to preprocess your page :
function yourthemename_preprocess_page(&$variables) {
$node = \Drupal::routeMatch()->getParameter('node');
if ($node) {
$variables['title'] = $node->getTitle();
}
}
and in your template page.html.twig
{{title}}

Answer 3

There are a couple of solutions to change the page title
On template
/**
* Implements hook_preprocess_HOOK().
*/
function MYMODULE_preprocess_page_title(&$variables) {
if ($YOUR_LOGIC == TRUE) {
$variables['title'] = 'New Title';
}
}
On the node view page
/**
* Implements hook_ENTITY_TYPE_view_alter().
*/
function mymodule_user_view_alter(array &$build, Drupal\Core\Entity\EntityInterface $entity, \Drupal\Core\Entity\Display\EntityViewDisplayInterface $display) {
if ($YOUR_LOGIC == TRUE) {
$build['#title'] = $entity->get('field_display_name')->getString();
}
}
for a sample if you want to change user title
function mymodule_user_view_alter(array &$build, Drupal\Core\Entity\EntityInterface $entity, \Drupal\Core\Entity\Display\EntityViewDisplayInterface $display) {
if ($entity->getEntityTypeId() == 'user') {
$build['#title'] = $entity->get('field_first_name')->getString();
}
}
On Controller or hook_form_alter
if ($YOUR_LOGIC == TRUE) {
$request = \Drupal::request();
if ($route = $request->attributes->get(\Symfony\Cmf\Component\Routing\RouteObjectInterface::ROUTE_OBJECT)) {
$route->setDefault('_title', 'New Title');
}
}

Answer 4

The Page Title is a block in Drupal 8. If you can find the plugin_id of the page title block (which is likely to be page_title_block), then you can override the title directly, with no need to change an existing twig template, using a block preprocessor. Your code may be similar to the following:
function vhs_preprocess_block(&$variables) {
// This example restricts based on the actual URL; you can replace this with any other logic you wish.
$request = \Drupal::request();
$uri = $request->getRequestUri();
if (
isset($variables['elements']['#base_plugin_id']) &&
$variables['elements']['#base_plugin_id'] == 'page_title_block' &&
isset($variables['content']['#title']['#markup']) &&
strpos($uri, '/url-to-match') === 0 // replace with logic that finds the correct page to override
) {
$variables['content']['#title']['#markup'] = 'My Custom Title';
}
}
The example above uses the Drupal request object to grab and compare the actual URL. The initial question asked to match based on the node path; you could get that with something like:
$current_path = \Drupal::service('path.current')->getPath();
Then, in place of the strpos condition above, you could use:
$current_path == 'node/12'

Answer 5

i have changed the page_title block for user/uid to a different custom account field name like this :
function hook_preprocess_block(&$variables) {
$path = \Drupal::request()->getpathInfo();
$arg = explode('/', $path);
if (isset($arg[2]) && $arg[2] == 'user' && isset($arg[3])) {
if (isset($variables['elements']['content']['#type']) && $variables['elements']['content']['#type'] == 'page_title') {
$account = \Drupal\user\Entity\User::load($arg[3]);
if(isset($account) && isset($account->field_mycustomfield->value)){
$variables['content']['#title']['#markup']=$account->field_mycustomfield->value;
}
}
}
}