YAML is used in TYPO3 for various configurations; most notable are
- Event listeners in
- Dependency injection information in
- Site configuration in
- System extension form configuration
- System extension rte_ckeditor configuration
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_PLACEHOLDERSdecides whether or not placeholders (
%abc%) will be resolved.
PROCESS_IMPORTSdecides whether or not imports (
importskey) will be resolved.
Use the method
to make use of the loader in your extensions:
use TYPO3\CMS\Core\Configuration\Loader\YamlFileLoader; // ... YamlFileLoader::load(string $fileName, int $flags = self::PROCESS_PLACEHOLDERS | self::PROCESS_IMPORTS)