Template for a wp-config.php file with included environment detection

wp-config.php

<?php
/**
 * The base configuration for WordPress
 *
 * @link https://codex.wordpress.org/Editing_wp-config.php
 *
 * @package WordPress
 */

// Defines the environment (prod|stage|dev)
if ( file_exists( __DIR__ . '/.env' ) ) {
	$env = trim( file_get_contents( __DIR__ . '/.env' ) );
	define( 'ENVIRONMENT', $env );
} else {
	echo 'Please add the <strong>.env</strong> file';
	exit;
}

// Setup environment specific database connection.
if ( 'prod' === ENVIRONMENT ) {
	define( 'DB_NAME', 'live_sitename' );
	define( 'DB_USER', 'live_user' );
	define( 'DB_PASSWORD', 'live_password' );
	define( 'DB_HOST', 'localhost' );
} elseif ( 'stage' === ENVIRONMENT ) {
	define( 'DB_NAME', 'stage_sitename' );
	define( 'DB_USER', 'stage_user' );
	define( 'DB_PASSWORD', 'stage_password' );
	define( 'DB_HOST', 'localhost' );
} else {
	define( 'DB_NAME', 'local_sitename' );
	define( 'DB_USER', 'local_user' );
	define( 'DB_PASSWORD', 'local_password' );
	define( 'DB_HOST', 'localhost' );
}

define( 'DB_CHARSET', 'utf8' );
define( 'DB_COLLATE', '' );
$table_prefix = 'abcd_';

/**
 * Authentication Unique Keys and Salts.
 *
 * @link https://api.wordpress.org/secret-key/1.1/salt/
 * @since 2.6.0
 */
define( 'AUTH_KEY',         $env . '(secret salt here)' );
define( 'SECURE_AUTH_KEY',  $env . '(secret salt here)' );
define( 'LOGGED_IN_KEY',    $env . '(secret salt here)' );
define( 'NONCE_KEY',        $env . '(secret salt here)' );
define( 'AUTH_SALT',        $env . '(secret salt here)' );
define( 'SECURE_AUTH_SALT', $env . '(secret salt here)' );
define( 'LOGGED_IN_SALT',   $env . '(secret salt here)' );
define( 'NONCE_SALT',       $env . '(secret salt here)' );

// Environment specific configuration.
if ( 'prod' === ENVIRONMENT ) {
	// Production settings.
	define( 'FORCE_SSL_ADMIN', true );
	define( 'WP_DEBUG', false );
	define( 'WP_DEBUG_DISPLAY', false );
	define( 'WP_DEBUG_CORE', false );
	define( 'WP_DEBUG_LOG', true );
} else {
	// Development and stage settings.
	define( 'WP_DEBUG', true );
	define( 'WP_DEBUG_DISPLAY', true );
	define( 'WP_DEBUG_CORE', false );
	define( 'WP_DEBUG_LOG', true );
}

// Global configuration, identical for all environments.
define( 'DISALLOW_FILE_EDIT', true );
define( 'DISALLOW_FILE_MODS', false );
define( 'WP_CRON_LOCK_TIMEOUT', '60' );
define( 'EMPTY_TRASH_DAYS', '30' );
define( 'WP_CACHE', true ); 

/* That's all, stop editing! Happy blogging. */

/** Absolute path to the WordPress directory. */
if ( ! defined( 'ABSPATH' ) )
	define( 'ABSPATH', dirname( __FILE__ ) . '/' );

/** Sets up WordPress vars and included files. */
require_once ABSPATH . 'wp-settings.php';