I have a legacy PHP project using a self-styled configuration file (globals.inc.php) which is generated by build scripts based on a template included in the code called globals.template.inc.php:

<?php

use MyPropject\Core\DBConn;

require_once __DIR__ . "/vendor/autoload.php";

/**
 * GLOBAL variables
 *
 */
define("I18N_FILES",         __DIR__ . '/i18n/lang_{LANGUAGE}.json');
define("I18N_CACHE",         __DIR__ . '/langcache/');
define("SITE_TITLE",         "¤SITE_TITLE¤");
define("SITE_NAME",          "¤SITE_NAME¤"); 
define("SITE_FQDN",          "¤SITE_FQDN¤");
define("SESSION_DURATION",   1800);
define("DEFAULT_FROM_EMAIL", "¤DEFAULT_FROM_EMAIL¤");
define("SESSION_NAME",       "¤SESSION_NAME¤"); 
define("CERT_LOCATION",      "¤CERT_LOCATION¤");
define("MYSQL_USERNAME",     "¤MYSQL_USERNAME¤");
define("MYSQL_PASSWORD",     "¤MYSQL_PASSWORD¤");
define("MYSQLDATABASENAME",  "¤MYSQL_DB_NAME¤");
define("MYSQL_HOSTNAME",     "¤MYSQL_HOSTNAME¤");
define("MYSQL_PORT",         ¤MYSQL_PORT¤);
define("MYSQL_DSN",          "mysql:dbname=" . MYSQLDATABASENAME . ";host=" . MYSQL_HOSTNAME. ";port=" . MYSQL_PORT);
define("DEPLOY_DATE",        "¤DEPLOY_DATE¤");
define("GIT_TAG_BACKEND",    "¤GIT_TAG_BACKEND¤");
define("GIT_TAG_FRONTEND",   "¤GIT_TAG_FRONTEND¤");
if (isset($_SERVER["SERVER_NAME"])) {
    define("IS_PROD", $_SERVER["SERVER_NAME"] === "www.MyPropject.com");
}

if (substr(SITE_TITLE, -1) == "¤" || substr(SITE_TITLE, -1) == "\xa4") {
    exit("Globals not set. Please run deploy.sh");
}
date_default_timezone_set('Europe/Berlin');

$mysqlConn = new mysqli(MYSQL_HOSTNAME, MYSQL_USERNAME, MYSQL_PASSWORD, MYSQLDATABASENAME, 3306);
if ($mysqlConn->connect_errno) {
    echo "Failed to connect to MySQL: (" . $mysqlConn->connect_errno . ") " . $mysqlConn->connect_error;
}
$mysqlConn->query("SET NAMES 'utf8'");

This has worked well over the years, but moving to newer versions of PHP and trying to adhere to some best practices and standards I am considering migrating to a .env file, among other reasons, because that approach seems to be more standard.

I find myself in a chicken-and-egg situation. I would like to be able to keep this configuration, since migrating everything in a big-bang would require revisiting all build jobs, a lot of classes, and many lines of PHP code referencing.

My proposition as a half-measure-transition is to do the following:

• Generate the .env file from the globals.inc.php by appending the below code to the file.
• Coding all new classes to use a central configuration class, which reads the .env file (vlucas/phpdotenv maybe)
• When all areas of the program use the .env file, rewrite the deploy scripts to generate the .env file

$envFileName = __DIR__ . "/.env";
function createEnvFile()
{
    global $envFileName;
    $contents = 
    "I18N_FILES=\"".I18N_FILES."\"\n".
    "I18N_CACHE=\"".I18N_CACHE."\"\n".
    "SITE_TITLE=\"".SITE_TITLE."\"\n".
    "SITE_NAME=\"".SITE_NAME."\"\n".
    "SITE_FQDN=\"".SITE_FQDN."\"\n".
    "SESSION_DURATION=\"".SESSION_DURATION."\"\n".
    "DEFAULT_FROM_EMAIL=\"".DEFAULT_FROM_EMAIL."\"\n".
    "SESSION_NAME=\"".SESSION_NAME."\"\n".
    "CERT_LOCATION=\"".CERT_LOCATION."\"\n".
    "MYSQL_USERNAME=\"".MYSQL_USERNAME."\"\n".
    "MYSQL_PASSWORD=\"".MYSQL_PASSWORD."\"\n".
    "MYSQLDATABASENAME=\"".MYSQLDATABASENAME."\"\n".
    "MYSQL_HOSTNAME=\"".MYSQL_HOSTNAME."\"\n".
    "MYSQL_PORT=\"".MYSQL_PORT."\"\n".
    "MYSQL_DSN=\"".MYSQL_DSN."\"\n".
    "DEPLOY_DATE=\"".DEPLOY_DATE."\"\n".
    "GIT_TAG_BACKEND=\"".GIT_TAG_BACKEND."\"\n".
    "GIT_TAG_FRONTEND=\"".GIT_TAG_FRONTEND."\"\n";
    file_put_contents($envFileName, $contents);

}

// check if .env file exists and has a timestamp similar to this file:
echo "checking for .env file in $envFileName";
if (file_exists($envFileName)) {
    // if file modification time is more than 10 minutes old, create a new one:
    if ( abs(filemtime(__FILE__) - filemtime($envFileName)) > 600 ){
        unlink($envFileName);
        createEnvFile();
    }
} else {
    createEnvFile();
}