Multiple WP environments with Dotenv and Composer

.env.development

DB_NAME=database
DB_USER=user
DB_PASSWORD=pass
DB_HOST=localhost
WP_HOME=http://example.dev
WP_SITEURL=http://example.dev/wp

wp-config.php

<?php

// Require Composer autoloader, which includes DotEnv
require_once __DIR__ . "/vendor/autoload.php";

/**
 * Check if environment exists in order of $stages array
 *
 * @return {String} $environment
 */
$environment = function() {
    $stages = array(
        "development",
        "staging",
        "production"
    );
    foreach ( $stages as $stage ) {
        if ( file_exists( __DIR__ . "/.env.$stage" ) ) {
            return $stage;
        }
    }
    return false;
};

/**
 * Use Dotenv to set stage
 */
if ( $stage = $environment() ) {
    Dotenv::load( __DIR__, ".env.$stage" );
} else {
    throw new \Exception( "Cannot load environment. Aborting mission." );
}

Dotenv::required(array(
    "DB_NAME",
    "DB_USER",
    "DB_PASSWORD",
    "DB_HOST",
    "WP_HOME",
    "WP_SITEURL"
));

/**
 * Activate debugging on development stage
 */
if ( $stage === "development" ) {
    define( "WP_DEBUG", true );
    define( "WP_CACHE", false );
} else {
    define( "WP_DEBUG", false );
    define( "WP_CACHE", true );
}

/**
 * Database
 */
define( "DB_NAME", getenv("DB_NAME") );
define( "DB_USER", getenv("DB_USER") );
define( "DB_PASSWORD", getenv("DB_PASSWORD") );
define( "DB_HOST", getenv("DB_HOST") );

/**
 * URLs
 */
define( "WP_HOME", getenv("WP_HOME") );
define( "WP_SITEURL", getenv("WP_SITEURL") );