TYPO3 v8 has reached its end-of-life March 31st, 2020 and is not maintained by the community anymore.

You can order Extended Long Term Support (ELTS) here: TYPO3 ELTS.

Configuration files

Files ext_tables.php and ext_localconf.php are the two most important files for the execution of extensions within TYPO3. They contain configuration used by the system on almost every request. They should therefore be optimized for speed.

  • ext_localconf.php is always included in global scope of the script, either frontend or backend.

    While you can put functions and classes into the script, it is a really bad practice because such classes and functions would always be loaded. It is better to have them included only as needed.

    So stick to changing values in $GLOBALS['TYPO3_CONF_VARS'] only!

  • ext_tables.php is not always included in global scope (in the frontend)

    It should still not contain functions and classes as it still very often loaded.

  • Use the API of class ExtensionManagementUtility for tasks such as adding tables, merging information into arrays, etc.

  • Before the inclusion of any of the two files, the variables $_EXTKEY is set to the extension key and $_EXTCONF is set to the configuration from $GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'][extension key]. We recommend to not use $_EXTKEY, current planning is to deprecate this variable in the future.

  • $TYPO3_LOADED_EXT[extension key] contains information about whether the module is loaded as local, global or system type, including the proper paths you might use, absolute and relative.

  • Your ext_tables.php and ext_localconf.php file must be designed so that they can safely be read and subsequently imploded into one single file with all the other configuration scripts!

  • You must never use a "return" statement in the files global scope - that would make the cached script concept break.

  • You must never use a "use" statement in the files global scope - that would make the cached script concept break and could conflict with other extensions.

  • You should not rely on the PHP constant __FILE__ for detection of include path of the script - the configuration might be executed from a cached script and therefore such information should be derived from e.g. \TYPO3\CMS\Core\Utility\GeneralUtility::getFileAbsFileName() or ExtensionManagementUtility::extPath().

Best practice for ext_tables.php and ext_localconf.php

It is a good practice to use call_user_func with an closure function. The following example contains the complete code:

defined('TYPO3_MODE') or die();

call_user_func(function () {
    // Add your code here

In most cases, the file ext_tables.php is no longer needed, since most of the code can be placed in Configuration\TCA\*.php files.