--- title: > What is deprecated code? pubDate: 2023-05-17 permalink: >- archive/2023/05/17/what-is-deprecated-code tags: - php - drupal - software-development --- Deprecating code is a way of identifying code that will be removed in a future major version. For example, the `drupal_set_message()` function was deprecated in Drupal 8.5 and removed in Drupal 9 as the `messenger` service replaced it. Once it was deprecated, the function was changed to use the new service to avoid duplicating code and a message was added to notify Developers: ```language-php function drupal_set_message($message = NULL, $type = 'status', $repeat = FALSE) { @trigger_error('drupal_set_message() is deprecated in Drupal 8.5.0 and will be removed before Drupal 9.0.0. Use \Drupal\Core\Messenger\MessengerInterface::addMessage() instead. See https://www.drupal.org/node/2774931', E_USER_DEPRECATED); $messenger = \Drupal::messenger(); if (isset($message)) { $messenger->addMessage($message, $type, $repeat); } return $messenger->all(); } ``` This approach means that code can be refactored without breaking backwards-compatibility and, to upgrade any custom code to be compatible with Drupal 9, any references to `drupal_set_message()` just needed to be updated to use the new Messenger service. No large rewrite needed!