Installation

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$ composer require symfony/dotenv

Usage

Sensitive information and environment-dependent settings should be defined as environment variables (as recommended for twelve-factor applications). Using a .env file to store those environment variables eases development and CI management by keeping them in one "standard" place and agnostic of the technology stack you are using (nginx vs PHP built-in server for instance).

Load a .env file in your PHP application via Dotenv::load():

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use Symfony\Component\Dotenv\Dotenv;

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

// You can also load several files
$dotenv->load(__DIR__.'/.env', __DIR__.'/.env.dev');

Given the following .env file content:

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# .env
DB_USER=root
DB_PASS=pass

Access the value with $_ENV in your code:

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$dbUser = $_ENV['DB_USER'];
// you can also use ``$_SERVER``

The load() method never overwrites existing environment variables. Use the overload() method if you need to overwrite them:

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// ...
$dotenv->overload(__DIR__.'/.env');

As you're working with the Dotenv component you'll notice that you might want to have different files depending on the environment you're working in. Typically this happens for local development or Continuous Integration where you might want to have different files for your test and dev environments.

You can use Dotenv::loadEnv() to ease this process:

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use Symfony\Component\Dotenv\Dotenv;

$dotenv = new Dotenv();
$dotenv->loadEnv(__DIR__.'/.env');

The Dotenv component will then look for the correct .env file to load in the following order whereas the files loaded later override the variables defined in previously loaded files:

1. If .env exists, it is loaded first. In case there's no .env file but a .env.dist, this one will be loaded instead.
2. If one of the previously mentioned files contains the APP_ENV variable, the variable is populated and used to load environment-specific files hereafter. If APP_ENV is not defined in either of the previously mentioned files, dev is assumed for APP_ENV and populated by default.
3. If there's a .env.local representing general local environment variables it's loaded now.
4. If there's a .env.$env.local file, this one is loaded. Otherwise, it falls back to .env.$env.

This might look complicated at first glance but it gives you the opportunity to commit multiple environment-specific files that can then be adjusted to your local environment. Given you commit .env, .env.test and .env.dev to represent different configuration settings for your environments, each of them can be adjusted by using .env.local, .env.test.local and .env.dev.local respectively.

You can adjust the variable defining the environment, default environment and test environments by passing them as additional arguments to Dotenv::loadEnv() (see loadEnv() for details).

You should never store a .env.local file in your code repository as it might contain sensitive information; create a .env file (or multiple environment-specific ones as shown above) with sensible defaults instead.

As a .env file is a regular shell script, you can source it in your own shell scripts:

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source .env

Add comments by prefixing them with #:

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# Database credentials
DB_USER=root
DB_PASS=pass # This is the secret password

Use environment variables in values by prefixing variables with $:

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DB_USER=root
DB_PASS=${DB_USER}pass # Include the user as a password prefix

Embed commands via $() (not supported on Windows):

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START_TIME=$(date)