Configuration Files (ext_tables.php & ext_localconf.php)

Rules and best practices

The following apply for both ext_tables.php and ext_localconf.php.

As a rule of thumb: Your ext_tables.php and ext_localconf.php files must be designed in a way that they can safely be read and subsequently imploded into one single file with all configuration of other extensions.

• You must not use a return statement in the file's global scope - that would make the cached script concept break.
• You must not rely on the PHP constant __FILE__ for detection of the include path of the script - the configuration might be executed from a cached file with a different location and therefore such information should be derived from, for example, \TYPO3\CMS\Core\Utility\GeneralUtility::getFileAbsFileName() or \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath().

• You must not wrap the file in a local namespace. This will result in nested namespaces.

  Diff of EXT:my_extension/ext_localconf.php | EXT:my_extension/ext_tables.php

  -namespace {
  -}

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• You can use use statements starting with TYPO3 v11.4:

  Diff of EXT:my_extension/ext_localconf.php | EXT:my_extension/ext_tables.php

  // you can use use:
  +use TYPO3\CMS\Core\Resource\Security\FileMetadataPermissionsAspect;
  +
  +$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['processDatamapClass'][] =
  +   FileMetadataPermissionsAspect::class;
  // Instead of the full class name:
  -$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['processDatamapClass'][] =
  -   \TYPO3\CMS\Core\Resource\Security\FileMetadataPermissionsAspect::class;

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• You can use declare(strict_types=1) and similar directives which must be placed at the very top of files. They will be stripped and added once in the concatenated cache file.

  Diff of EXT:my_extension/ext_localconf.php | EXT:my_extension/ext_tables.php

  // You can use declare strict and other directives
  // which must be placed at the top of the file
  +declare(strict_types=1);

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• You must not check for values of the removed TYPO3_MODE or TYPO3_REQUESTTYPE constants (for example, if (TYPO3_MODE === 'BE')) or use the \TYPO3\CMS\Core\Http\ApplicationType enum within these files as it limits the functionality to cache the whole configuration of the system. Any extension author should remove the checks, and re-evaluate if these context-depending checks could go inside the hooks / caller function directly, for example, do not:

  Diff of EXT:my_extension/ext_localconf.php | EXT:my_extension/ext_tables.php

  // do NOT do this:
  -if (TYPO3_MODE === 'BE')

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• You should check for the existence of the constant defined('TYPO3') or die(); at the top of ext_tables.php and ext_localconf.php files right after the use statements to make sure the file is executed only indirectly within TYPO3 context. This is a security measure since this code in global scope should not be executed through the web server directly as entry point.

  EXT:my_extension/ext_localconf.php | EXT:my_extension/ext_tables.php

  <?php
  declare(strict_types=1);
  
  use TYPO3\CMS\Core\Utility\ExtensionManagementUtility;
  
  // put this at top of every ext_tables.php and ext_localconf.php right after
  // the use statements
  defined('TYPO3') or die();

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• You must use the extension name (for example, "tt_address") instead of $_EXTKEY within the two configuration files as this variable is no longer loaded automatically.
• However, due to limitations in the TYPO3 Extension Repository, the $_EXTKEY option must be kept within an extension's ext_emconf.php file.
• You do not have to use a directly called closure function after dropping TYPO3 v10.4 support.

The following example contains the complete code:

<?php

declare(strict_types=1);

use MyVendor\MyExtension\MyClass;

defined('TYPO3') or die();

// Add your code here
MyClass::doSomething();

Additionally, it is possible to extend TYPO3 in a lot of different ways (adding TCA, backend routes, Symfony console commands, etc), which do not need to touch these files.