Create custom Symfony translation extractor

Licensed under Creative Commons.


The Symfony translation component allows you to extract translations from your PHP codebase & Twig templates into the translation file format of your liking, for example .po files.

The documentation describes it like this:

The most time-consuming tasks when translating an application is to extract all the template contents to be translated and to keep all the translation files in sync. Symfony includes a command called translation:update that helps you with these tasks.

But what if not all my translations are hardcoded in code or templates, and some - or all - are dynamic? For example loaded from an external data source, like a REST API.

Create translation extractor

You can add your own translation extractor. Which will be run when executing the Symfony consoles’ translation:update command. In addition to the extractors that are already included.

Create a class that implements the ExtractorInterface:



namespace App\Translation;

use Symfony\Component\Translation\Extractor\ExtractorInterface;
use Symfony\Component\Translation\MessageCatalogue;

 * Extracts custom translation strings.
 * **@package ***App*\Translation
*class TranslationsExtractor implements ExtractorInterface {

   * Prefix for new found message.
   * **@var **string
  *private $prefix = '';

   * Returns the translation messages.
   * **@return **string[]
   *   All messages.
  *protected function getMessages(): array {
    $messages = [];

    // *TODO: Get all your translation strings here.
    *return $messages;

   * Extracts translation messages to the catalogue.
   * **@param **string|array $resource
   *   Files, a file or a directory.
   * **@param **\Symfony\Component\Translation\MessageCatalogue $catalogue
   *   The message catalogue.
  *public function extract($resource, MessageCatalogue $catalogue) {
    foreach ($this->getMessages() as $message) {
      $catalogue->set($message, $this->prefix . $message);

   * {**@inheritdoc**}
  *public function setPrefix(string $prefix) {
    $this->prefix = $prefix;


Tag it with name=translation.extractor & an alias.

# config/services.yml
    class: App\Translation\TranslationsExtractor
      - { name: translation.extractor, alias: custom }

This was written using Symfony version 5.1.6.

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