ext_tables.php

<?php
namespace Tx\Myutils\Utility;

/*                                                                        *
 * This script belongs to the TYPO3 Extension "myutils".                  *
 *                                                                        *
 * It is free software; you can redistribute it and/or modify it under    *
 * the terms of the GNU General Public License, either version 3 of the   *
 * License, or (at your option) any later version.                        *
 *                                                                        *
 * The TYPO3 project - inspiring people to share!                         *
 *                                                                        */

use TYPO3\CMS\Core\SingletonInterface;

/**
 * This class contains utility functions for language file handling.
 */
class LanguageUtility implements SingletonInterface {

	/**
	 * Following snippet lets you easily override XLIFF-based localization files for any extension.
	 *
	 * Create localization files within your extension in:
	 *
	 * Resources/Private/Language/Overrides/<extension-key>.<original-name>.xlf
	 * Resources/Private/Language/Overrides/<locale>.<extension-key>.<original-name>.xlf
	 *
	 * E.g., you want to override EXT:news/Resources/Private/Language/locallang_db.xlf, then create
	 *
	 * Resources/Private/Language/Overrides/news.locallang_db.xlf
	 *
	 * and, to override the French localization:
	 *
	 * Resources/Private/Language/Overrides/fr.news.locallang_db.xlf
	 *
	 * BEWARE: In order for French (or any other language) override to work, you MUST have the original
	 * French localization for the corresponding extension.
	 *
	 * Call this method in a ext_tables.php file.
	 *
	 * @see https://gist.github.com/xperseguers/99163ef8b01edb8f5333
	 * @author Xavier Perseguers xperseguers
	 */
	public function overrideLanguageFiles() {

		$languageOverridePath = \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('myutils') . 'Resources/Private/Language/Overrides/';
		$extensionRelativePath = substr($languageOverridePath, strlen(PATH_site));

		$languageFiles = \TYPO3\CMS\Core\Utility\GeneralUtility::getFilesInDir($languageOverridePath, 'xlf');
		foreach ($languageFiles as $file) {
			$parts = explode('.', $file);

			if (count($parts) === 3) {
				$locale = 'default';
				$extensionKey = $parts[0];
				$languageFileWithoutExtension = $parts[1];
			} elseif (count($parts) === 4) {
				$locale = $parts[0];
				$extensionKey = $parts[1];
				$languageFileWithoutExtension = $parts[2];
			} else {
				throw new \RuntimeException('The file located at ' . $languageOverridePath . $file . ' can  not be used for overriding a language file. Please see LangaugeUtility::overrideLanguageFiles() for details.');
				continue;
			}

			$originalLanguageFileName = $this->detectOriginalLanguageFile($extensionKey, $languageFileWithoutExtension);
			if (!isset($originalLanguageFileName)) {
				throw new \RuntimeException('Original file for Override ' . $file . ' could not be found.');
			}

			// We need to add the absolute file to the override configuration as well because
			// some extension already to a getFileAbsFileName() before calling the localization
			// utility. In that case the "EXT:" prefixed version will not work for the override.
			$originalLanguageFileNameAbsolute = \TYPO3\CMS\Core\Utility\GeneralUtility::getFileAbsFileName($originalLanguageFileName);

			if ($locale === 'default') {
				// Register overlay for English localization file
				$GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride'][$originalLanguageFileName][] = $extensionRelativePath . $file;
				$GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride'][$originalLanguageFileNameAbsolute][] = $extensionRelativePath . $file;
			} else {
				// Register overlay for a given locale localization file
				$GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride'][$locale][$originalLanguageFileName][] = $extensionRelativePath . $file;
				$GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride'][$locale][$originalLanguageFileNameAbsolute][] = $extensionRelativePath . $file;
			}
		}
	}

	/**
	 * Tries to detect the original language file by looping over all possible Extensions.
	 *
	 * @param string $extensionKey
	 * @param string $languageFileWithoutExtension
	 * @return string
	 */
	protected function detectOriginalLanguageFile($extensionKey, $languageFileWithoutExtension) {

		$originalLanguageFileName = NULL;

		foreach (array('.xlf', '.xml') as $possibleExtension) {
			$possibleOriginalFile = 'EXT:' . $extensionKey . '/Resources/Private/Language/' . $languageFileWithoutExtension . $possibleExtension;
			$possibleOriginalFileAbsolute = \TYPO3\CMS\Core\Utility\GeneralUtility::getFileAbsFileName($possibleOriginalFile);
			if (is_file($possibleOriginalFileAbsolute)) {
				$originalLanguageFileName = $possibleOriginalFile;
				break;
			}
		}

		if (!isset($originalLanguageFileName) && $extensionKey === 'lang' && file_exists(\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('lang') . $languageFileWithoutExtension . '.xlf')) {
			$originalLanguageFileName = 'EXT:' . $extensionKey . '/' . $languageFileWithoutExtension . '.xlf';
		}

		return $originalLanguageFileName;
	}
}