Attention

TYPO3 v9 has reached its end-of-life September 30th, 2021 and is not maintained by the community anymore. Looking for a stable version? Use the version switch on the top left.

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

YAML API

YAML is used in TYPO3 for various configurations; most notable are

YamlFileLoader

TYPO3 is using a custom YAML loader for handling YAML in TYPO3 based on the Symfony YAML package. It's located at \TYPO3\CMS\Core\Configuration\Loader\YamlFileLoader and can be used when YAML parsing is required.

The TYPO3 Core YAML resolves environment variables. Resolving of variables in the loader can be enabled or disabled via flags. For example, when editing the site configuration through the backend interface the resolving of environment variables needs to be disabled to be able to add environment configuration through the interface.

The format for environment variables is %env(ENV_NAME)%. Environment variables may be used to replace complete values or parts of a value.

The YAML Loader class has two flags: PROCESS_PLACEHOLDERS and PROCESS_IMPORTS.

  • PROCESS_PLACEHOLDERS decides whether or not placeholders (%abc%) will be resolved.

  • PROCESS_IMPORTS decides whether or not imports (imports key) will be resolved.

Use the method YamlFileLoader::load() to make use of the loader in your extensions:

use TYPO3\CMS\Core\Configuration\Loader\YamlFileLoader;

// ...

(new YamlFileLoader())->load(string $fileName, int $flags = self::PROCESS_PLACEHOLDERS | self::PROCESS_IMPORTS)