Environment Variables

Symfony will grab any environment variable prefixed with ``SYMFONY__`` and

set it as a parameter in the service container. Some transformations are

applied to the resulting parameter name:

* ``SYMFONY__`` prefix is removed;

* Parameter name is lowercased;

* Double underscores are replaced with a period, as a period is not

a valid character in an environment variable name.

For example, if you're using Apache, environment variables can be set using the

`SetEnv`_ directive with the following ``VirtualHost`` configuration:

..code-block::apache

For Nginx web servers, the environment variables can be set with the `fastcgi_param`_

directive. For example, in the configuration file where the ``fastcgi_params``

file is included:

..code-block::nginx

..versionadded::3.2

``env()`` parameters were introduced in Symfony 3.2.

..note::

The examples above are for an Apache and Nginx configuration. However, this

will work for any web server which supports the setting of environment

variables.

Also, in order for your console to work (which does not use a web server),

you must export these as shell variables. On a Unix system, you can run

the following:

..code-block::terminal

You can reference environment variables by using special parameters named after

the variables you want to use enclosed between ``env()``. Their actual values

will be resolved at runtime (once per request), so that dumped containers can be

reconfigured dynamically even after being compiled.

Now that you have declared an environment variable, it will be present

in the PHP ``$_SERVER`` global variable. Symfony then automatically sets all

``$_SERVER`` variables prefixed with ``SYMFONY__`` as parameters in the service

container.

You can now reference these parameters wherever you need them.

For example, if you want to use the value of the ``DATABASE_HOST`` environment

variable in you service container configuration, you can reference it using

``%env(DATABASE_HOST)%`` in your configuration files:

..configuration-block::

..code-block::yaml

..code-block::xml

..code-block::php

You can also give the ``env()`` parameters a default value: the default value

will be used whenever the corresponding environment variable is *not* found:

..configuration-block::

..code-block::yaml

..code-block::xml

..code-block::php

Setting environment variables is generally done at the web server level or in the

terminal. If you're using Apache, Nginx or just the console, you can use e.g. one

of the following:

..configuration-block::

..code-block::apache

..code-block::nginx

..code-block::terminal

..tip::

You can also define the default value of any existing parameters using

special environment variables named after their corresponding parameter

prefixed with ``SYMFONY__`` after replacing dots by double underscores

(e.g. ``SYMFONY__KERNEL__CHARSET`` to set the default value of the

``kernel.charset`` parameter). These default values are resolved when

compiling the service container and won't change at runtime once dumped.

Constants