Escaping a PHP function as an Array value - php

Question

I'm working on a Drupal 8 starter kit with Composer, similar to drupal-composer/drupal-project.
In my post-install script, I want to re-generate a settings.php file with my custom values.
I've seen that can be done with the drupal_rewrite_settings function.
For example, I'm rewriting the config_sync_directory value like that :
require_once $drupalRoot . '/core/includes/bootstrap.inc';
require_once $drupalRoot . '/core/includes/install.inc';
new Settings([]);
$settings['settings']['config_sync_directory'] = (object) [
'value' => '../config/sync',
'required' => TRUE,
];
drupal_rewrite_settings($settings, $drupalRoot . '/sites/default/settings.php');
Problem is I want my Drupal 8 project to have a Dotenv so the maintainers don't have to modify the settings.php but only a .env file in the root folder of the project. To make it work, my settings.php must look like this :
$databases['default']['default'] = [
'database' => getenv('MYSQL_DATABASE'),
'driver' => 'mysql',
'host' => getenv('MYSQL_HOSTNAME'),
'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
'password' => getenv('MYSQL_PASSWORD'),
'port' => '',
'prefix' => '',
'username' => getenv('MYSQL_USER'),
];
$settings['trusted_host_patterns'] = explode(',', '^'.getenv('SITE_URL').'$');
As you can see, the values are replaced by PHP functions, and I can't see a good way to print those values, to the point I'm not even sure that's possible.
So my question is : is it possible to escape a PHP function as an Array value when declaring this variable ?

Answer 1

Looks like it's not possible because of the way the Drupal function works.
Solution 1 by #misorude
Using the drupal_rewrite_settings function, we can add the value of settings as a String, like this :
$settings['settings']['trusted_host_patterns'] = (object) [
'value' => "FUNC[explode(',', '^'.getenv('SITE_URL').'$')]",
'required' => TRUE,
];
And after that, we can replace all occurrences of "FUNC[***]" by *** directly in the settings.php file.
Solution 2
Put all your settings in a separate file. Example here, a custom.settings.php file :
if (getenv('DEBUG') == 'true') {
$settings['container_yamls'][] = DRUPAL_ROOT . '/sites/dev.services.yml';
$config['system.performance']['css']['preprocess'] = FALSE;
$config['system.performance']['js']['preprocess'] = FALSE;
}
$databases['default']['default'] = [
'database' => getenv('MYSQL_DATABASE'),
'driver' => 'mysql',
'host' => getenv('MYSQL_HOSTNAME'),
'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
'password' => getenv('MYSQL_PASSWORD'),
'port' => '',
'prefix' => '',
'username' => getenv('MYSQL_USER'),
];
$settings['trusted_host_patterns'] = explode(',', '^'.getenv('SITE_URL').'$');
$settings['file_private_path'] = 'sites/default/files/private';
$settings['config_sync_directory'] = '../config/sync';
Then we can copy the default.settings.php and add our custom settings.
$fs = new Filesystem();
$settings_generated = $drupalRoot . '/sites/default/settings.php';
$settings_default = $drupalRoot . '/sites/default/default.settings.php';
$settings_custom = $drupalRoot . '/../includes/custom.settings.php';
$fs->remove($settings_generated);
$fs->dumpFile($settings_generated, file_get_contents($settings_default) . file_get_contents($settings_custom));
There's also a appendToFile method that seems way better than dumping a new file with dumpFile, but it was not working unfortunatly.