Inside TYPO3

3.8.3. How translations are handled by the system

Here is the basic facts about TYPO3s technology to handle localization of the backend interface:

1. Default language: The default language of TYPO3 is English. (Please respect this in extensions as well!)

2. Alternative languages: The list of available system languages is defined in the constant TYPO3_languages (hardcoded/defined in config_default.php). This "list" is two-char identification codes representing languages. The code usually reflects a ccTLD related to the language but can be any unique 2-char combination.

1. Label files: All labels for the backend (and frontend) are stored in "locallang-XML" (llXML) files located in extensions. They are named according to the scheme "locallang*.xml". The default labels must be english! The system extension "lang" contains labels for the core system.

   1. Notice: "locallang*.php" files is an old alternative still supported but deprecated; They contain the $LOCAL_LANG array in a PHP script which is simply included. Old "locallang.php" files can be converted to llXML files using the extension "extdeveval"

2. Localization methods: The "language" class (from sysext/lang/lang.php) contains methods for requesting labels out of llXML files in the backend (such as getLL() and sL()). The language class also contains an instance of the class "t3lib_cs" where the charsets used for each language are defined. The charset is detected by the "template" class and automatically set for the documents in the backend.

3. Translation of llXML files: On a local system this is handled by the extension "llxmltranslate". Unless the llXML files contains inline translation or a specific reference to an external file, the "llxmltranslate" tool will write the translation to a corresponding filename in "typo3conf/l10n/[language key]/[extension key]" (recommended).

4. Language packs: Due to the large amount of languages for TYPO3 (more than 40) all llXML files in the core and extensions should contain only the default english labels. If no entry is found in the main file for translations, automatically a translation is looked for in "typo3conf/l10n/[language key]/[extension key]". The directory "typo3conf/l10n/[language key]/" is called the "language pack".

For more detailed information about Frontend localization in TYPO3, please refer to the document "Frontend Localization Guide" (doc_l10nguide).