Contributed by
Fabien Potencier
in #21234.

A common practice when developing applications is to store some configuration options as environment variables in a .env file (pronounced "dot-env"). You can already use this technique in Symfony applications, but in Symfony 3.3 we've decided to make it a built-in feature thanks to the new Dotenv component.

In practice, the Dotenv component parses .env files to make environment variables stored in them accessible in your application via getenv(), $_ENV or $_SERVER. If your .env file contains these variables:

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DB_USER=root
DB_PASS=pass

The following code will parse them and turn them into environment variables:

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use Symfony\Component\Dotenv\Dotenv;

(new Dotenv())->load(__DIR__.'/.env');

Now you can get the database password in your application as follows:

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$dbPassword = getenv('DB_PASS');

In addition to loading the variables, you can just parse them because the component defines three stages: load, parse, and populate.

Before creating a new component, we reviewed the existing libraries that provide similar features, but none of them matched our specific set of requirements:

  • Variables should not be validated in any way (because the real environment variables can only be strings and you can't validate them).
  • The component provides a strict implementation of what you can do in a real bash shell script and nothing more: $VAR and ${VAR} are supported, you can concatenate strings, execute commands and store the result in a variable, etc.
  • Superb error messages to easily spot any issue.
  • Clean and minimal API, without unneeded abstractions like being able to add an environment variable directly (just use putenv()).