Symfony\Component\Translation\Translator::optimizeCatalogue PHP Method

    private function optimizeCatalogue($locale)
    {
        if (strlen($locale) > 3) {
            $fallback = substr($locale, 0, -strlen(strrchr($locale, '_')));
        } else {
            $fallback = $this->fallbackLocale;
        }

        if (!$fallback) {
            return;
        }

        if (!isset($this->catalogues[$fallback])) {
            $this->loadCatalogue($fallback);
        }

        $this->catalogues[$locale]->addFallbackCatalogue($this->catalogues[$fallback]);
    }