yii2-swiftmailer/apps/advanced/environments/index.php

<?php
/**
 * The manifest of files that are local to specific environment.
 * This file returns a list of environments that the application
 * may be installed under. The returned data must be in the following
 * format:
 *
 * ```php
 * return array(
 *     'environment name' => array(
 *         'path' => 'directory storing the local files',
 *         'writable' => array(
 *             // list of directories that should be set writable
 *         ),
 *     ),
 * );
 * ```
 */
return [
	'Development' => [
		'path' => 'dev',
		'writable' => [
			// handled by composer.json already
		],
		'executable' => [
			'yii',
		],
	],
	'Production' => [
		'path' => 'prod',
		'writable' => [
			// handled by composer.json already
		],
		'executable' => [
			'yii',
		],
	],
];