TYPO3 / TYPO3.CMS

            $languageFactory = GeneralUtility::makeInstance(LocalizationFactory::class);

            $this->LOCAL_LANG = $languageFactory->getParsedData($languageFilePath, $this->LLkey);

            $alternativeLanguageKeys = GeneralUtility::trimExplode(',', $this->altLLkey, true);

            foreach ($alternativeLanguageKeys as $languageKey) {

                $tempLL = $languageFactory->getParsedData($languageFilePath, $languageKey);

                if ($this->LLkey !== 'default' && isset($tempLL[$languageKey])) {

                    $this->LOCAL_LANG[$languageKey] = $tempLL[$languageKey];

                }

            }

            // Overlaying labels from TypoScript (including fictitious language keys for non-system languages!):

            if (isset($this->conf['_LOCAL_LANG.'])) {

                // Clear the "unset memory"

            $languageFactory = GeneralUtility::makeInstance(LocalizationFactory::class);

            $this->LOCAL_LANG = $languageFactory->getParsedData($locallangPathAndFilename, $this->languageKey);

            foreach ($this->alternativeLanguageKeys as $language) {

                $tempLL = $languageFactory->getParsedData($locallangPathAndFilename, $language);

                if ($this->languageKey !== 'default' && isset($tempLL[$language])) {

                    $this->LOCAL_LANG[$language] = $tempLL[$language];

                }

            }

        }

        $this->loadTypoScriptLabels();

    }