When dealing with sensitive options, like database credentials, we also recommend

that you store them outside the Symfony project and make them available

through environment variables. Learn how to do it in the following article:

:doc:`/configuration/external_parameters`.

through environment variables:

..code-block::yaml

..versionadded::3.2

Support for runtime environment variables via the ``%env(...)%`` syntax was

added in Symfony 3.2. Prior to version 3.2, you needed to use the

:doc:`special SYMFONY__ variables</configuration/external_parameters>`.

.. _`feature toggles`:https://en.wikipedia.org/wiki/Feature_toggle

.. _`constant() function`:http://twig.sensiolabs.org/doc/functions/constant.html