Config Mapping

The base image includes a declarative mechanism to configure TYPO3 entirely via environment variables. This is implemented in base/config/typo3/additional.php.

How It Works

The additional.php file defines a $configMappings array that maps environment variable names to TYPO3 configuration paths. At runtime, each environment variable is checked — if set, its value is written into the corresponding TYPO3 configuration key.

This means you can configure database connections, mail transport, cache backends, and more without editing any PHP files.

The Mapping Array

The mapping uses a nested structure that mirrors TYPO3's configuration hierarchy:

$configMappings = [
    'DB' => [
        'Connections' => [
            'Default' => [
                'host'     => 'TYPO3_DB_HOST',
                'port'     => 'TYPO3_DB_PORT',
                'dbname'   => 'TYPO3_DB_NAME',
                'user'     => 'TYPO3_DB_USERNAME',
                'password' => 'TYPO3_DB_PASSWORD',
                'driver'   => 'TYPO3_DB_DRIVER',
                'charset'  => 'TYPO3_DB_CHARSET',
            ],
        ],
    ],
    'SYS' => [
        'sitename'           => 'TYPO3_PROJECT_NAME',
        'encryptionKey'      => 'TYPO3_ENCRYPTION_KEY',
        'trustedHostsPattern'=> 'TYPO3_TRUSTED_HOSTS_PATTERN',
        'displayErrors'      => 'TYPO3_DISPLAY_ERRORS',
    ],
    // ... more mappings for MAIL, GFX, EXTENSIONS
];

Adding Custom Mappings

To map a new environment variable, extend the $configMappings array. For example, to configure an extension setting:

$configMappings = [
    'EXTENSIONS' => [
        'my_extension' => [
            'apiKey'    => 'MY_EXTENSION_API_KEY',
            'debugMode' => 'MY_EXTENSION_DEBUG',
        ],
    ],
    // ... existing mappings
];

Then set the environment variable in your docker-compose.yml or .env file:

environment:
  MY_EXTENSION_API_KEY: "your-api-key"

Overriding Entirely

If you need full control, mount your own configuration file:

volumes:
  - ./my-additional.php:/var/www/html/config/system/additional.php

This replaces the built-in mapping entirely.

Redis Cache Backend

The Redis cache backend is configured automatically when REDIS_HOST is set. It maps TYPO3 cache backends to Redis databases:

Cache	Redis DB
`hash`	0
`pages`	1
`rootline`	2