TYPO3_DB compatibility layer for TYPO3 v9.x
Until TYPO3 core v8, the low level database API was provided by a class called t3lib_db - later renamed to TYPO3\CMS\Core\Database\DatabaseConnection - and populated in global scope as $GLOBALS['TYPO3_DB'].
The class managed connections and queries to mysql database endpoints and the two additional extensions "dbal" and "adodb" were available to support further different DBMS in TYPO3.
With TYPO3 v8 however, the database API was rewritten and is now based on doctrine-dbal. All queries in the TYPO3 v8 core were rewritten to that new API, keeping the old $GLOBALS['TYPO3_DB'] API working in parallel as backwards compatible layer for extensions.
With TYPO3 v9, the old $GLOBALS['TYPO3_DB'] based database API has been extracted from the core to this extension "typo3db_legacy". It provides the same functionality as what has been supported by the core in v8 and can be used as a backwards compatible layer for extensions that still did not move to the new doctrine based API. So those extensions still work with TYPO3 v9.
The latest version can be installed via TER (https://typo3.org) or via composer by adding ''composer require friendsoftypo3/typo3db-legacy'' in a TYPO3 v9 installation.
If an extension should be compatible with both TYPO3 v8 and TYPO3 v9 and relies in v9 on typo3db_legacy, it should list typo3db_legacy as 'suggests' dependency in it's ext_emconf.php file. This way, the dependency is optional and needs to be manually loaded by an administrator in the TYPO3 v9 backend, but the core still ensures typo3db_legacy is loaded before the affected extension:
'constraints' => [ ... 'suggests' => [ 'typo3db_legacy' => '1.0.0-1.0.99', ], ],
Extensions that dropped support for TYPO3 v8 (or keeps separate branches) and did not migrate to doctrine in its v9 version, should list typo3db_legacy in the 'depends' section of ext_emconf.php:
'constraints' => [ ... 'depends' => [ 'typo3db_legacy' => '1.0.0-1.1.99', ], ],
The extension consumes the same 'Default' configuration from TYPO3_CONF_VARS as the doctrine based API. The connection is initialized in the extension's ext_localconf.php file.
The latest version here reflects a feature-complete state. There are bugs, we know, there are possible feature requests - we know. But it's highly likely that this extension gets no new features, unless somebody steps up and continues the development (see further below).
Feel free to submit any pull request, or add documentation, tests, as you please. We will publish a new version every once in a while, depending on the amount of changes and pull requests submitted.
If you want to keep adding features, and keep typo3db_legacy compatible with the latest TYPO3 versions, feel free to contact Benni Mack.
The extension is published under GPL v2+, all included third-party libraries are published under their respective licenses.
A lot of contributors have been working on this area while this functionality was part of the TYPO3 Core. This package is now maintained by a loose group of TYPO3 enthusiasts inside the TYPO3 Community. Feel free to contact Benni Mack (email@example.com) for any questions regarding "typo3db_legacy".