wp-config.load.php

<?php
/**
 * WordPress Multi-Environment Config - Load config settings
 *
 * @package    Studio 24 WordPress Multi-Environment Config
 * @version    2.0.1 (x-release-please-version)
 * @author     Studio 24 <hello@studio24.net>
 */

function s24_load_environment_config() {

    /**
     * Setup environment
     */
    // Set env if set via environment variable
    if (getenv('WP_ENV') !== false) {
        define('WP_ENV', preg_replace('/[^a-z]/', '', getenv('WP_ENV')));
    }

    // Set env via --env=<environment> argument if running via WP-CLI
    if (!defined('WP_ENV') && PHP_SAPI == "cli" && defined('WP_CLI_ROOT')) {

        // We need to set $argv as global to be able to access it
        global $argv;

        if (isset($argv)) {
            foreach ($argv as $arg) {
                if (preg_match('/--env=(.+)/', $arg, $m)) {
                    define('WP_ENV', preg_replace('/[^a-z]/', '', $m[1]));
                    break;
                }
            }
        }

        // Also support via .env file in config directory
        if (!defined('WP_ENV')) {
            if (file_exists(__DIR__ . '/.env')) {
                $environment = trim(file_get_contents(__DIR__ . '/.env'));
                define('WP_ENV', preg_replace('/[^a-z]/', '', $environment));
            }
        }
    }

    // Define ENV from hostname
    if (!defined('WP_ENV')) {
        if (isset($_SERVER['HTTP_X_FORWARDED_HOST']) && !empty($_SERVER['HTTP_X_FORWARDED_HOST'])) {
            $hostname = strtolower(filter_var($_SERVER['HTTP_X_FORWARDED_HOST'], FILTER_SANITIZE_STRING));
        } else {
            $hostname = strtolower(filter_var($_SERVER['HTTP_HOST'], FILTER_SANITIZE_STRING));
        }
    }

    // Load environments
    require  __DIR__ . '/wp-config.env.php';

    if (!isset($env) || !is_array($env)) {
        throw new Exception('$env array not detected, you must set this in wp-config.env.php');
    }

    // Set environment constants
    if (defined('WP_ENV')) {
        if (isset($env[WP_ENV])) {
            define('WP_ENV_DOMAIN', $env[WP_ENV]['domain']);
            define('WP_ENV_PATH', trim($env[WP_ENV]['path'], '/'));
            define('WP_ENV_SSL', (bool) $env[WP_ENV]['ssl']);
        }

    } else {

        // Detect environment from hostname
        foreach ($env as $environment => $env_vars) {
            if (!isset($env_vars['domain'])) {
                throw new Exception('You must set the domain value in your environment array, see wp-config.env.php');
            }
            $domain = $env_vars['domain'];

            $wildcard = (is_string($domain) && strpos($domain, '*') !== false) ? true : false;
            if ($wildcard) {
                $match = '/' . str_replace('\*', '([^.]+)', preg_quote($domain, '/')) . '/';
                if (preg_match($match, $hostname, $m)) {
                    if (!defined('WP_ENV')) {
                        define('WP_ENV', preg_replace('/[^a-z]/', '', $environment));
                    }
                    define('WP_ENV_DOMAIN', str_replace('*', $m[1], $domain));
                    if (isset($env_vars['ssl'])) {
                        define('WP_ENV_SSL', (bool)$env_vars['ssl']);
                    } else {
                        define('WP_ENV_SSL', false);
                    }
                    if (isset($env_vars['path'])) {
                        define('WP_ENV_PATH', trim($env_vars['path'], '/'));
                    }

                    /**
                    * Define WordPress Site URLs
                    */
                    $protocol = (WP_ENV_SSL) ? 'https://' : 'http://';
                    $path = (defined('WP_ENV_PATH')) ? '/' . trim(WP_ENV_PATH, '/') : '';

                    if (!defined('WP_SITEURL')) {
                        define('WP_SITEURL', $protocol . trim(WP_ENV_DOMAIN, '/') . $path);
                    }
                    if (!defined('WP_HOME')) {
                        define('WP_HOME', $protocol . trim(WP_ENV_DOMAIN, '/') . $path);
                    }
                    break;
                }
            }
            if (!is_array($domain)) {
                $domain = [$domain];
            }
            foreach ($domain as $domain_name) {
                if ($hostname === $domain_name) {
                    if (!defined('WP_ENV')) {
                        define('WP_ENV', preg_replace('/[^a-z]/', '', $environment));
                    }
                    define('WP_ENV_DOMAIN', $domain_name);
                    if (isset($env_vars['ssl'])) {
                        define('WP_ENV_SSL', (bool)$env_vars['ssl']);
                    } else {
                        define('WP_ENV_SSL', false);
                    }
                    if (isset($env_vars['path'])) {
                        define('WP_ENV_PATH', trim($env_vars['path'], '/'));
                    }

                    /**
                    * Define WordPress Site URLs
                    */
                    $protocol = (WP_ENV_SSL) ? 'https://' : 'http://';
                    $path = (defined('WP_ENV_PATH')) ? '/' . trim(WP_ENV_PATH, '/') : '';

                    if (!defined('WP_SITEURL')) {
                        define('WP_SITEURL', $protocol . trim(WP_ENV_DOMAIN, '/') . $path);
                    }
                    if (!defined('WP_HOME')) {
                        define('WP_HOME', $protocol . trim(WP_ENV_DOMAIN, '/') . $path);
                    }
                    break;
                }
            }
        }
    }

    if (!defined('WP_ENV')) {
        throw new Exception("Cannot determine current environment");
    }
    if (!defined('WP_ENV_DOMAIN')) {
        throw new Exception("Cannot determine current environment domain, make sure this is set in wp-config.env.php");
    }
    if (!defined('WP_ENV_SSL')) {
        define('WP_ENV_SSL', false);
    }
    if (WP_ENV_SSL && (!defined('FORCE_SSL_ADMIN'))) {
        define('FORCE_SSL_ADMIN', true);
    }

    // Define W3 Total Cache hostname
    if (defined('WP_CACHE')) {
        define('COOKIE_DOMAIN', $hostname);
    }

}
s24_load_environment_config();


/**
 * Load config
 */

// 1st - Load default config
require  __DIR__ . '/wp-config.default.php';

// 2nd - Load config file for current environment
require  __DIR__ . '/wp-config.' . WP_ENV . '.php';

// 3rd - Load local config file with any sensitive settings
if (file_exists( __DIR__ . '/wp-config.local.php')) {
    require  __DIR__ . '/wp-config.local.php';
}