> For the complete documentation index, see [llms.txt](https://quantumphp.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://quantumphp.gitbook.io/docs/packages/config/usage.md).

# Usage

## Import a normal package config file

This is the common Quantum pattern.

```php
use Quantum\Loader\Setup;

config()->import(new Setup('config', 'mailer'));

$defaultAdapter = config()->get('mailer.default');
$smtpHost = config()->get('mailer.smtp.host');
```

Use `import()` when the file should live under its own top-level section.

## Load one file as the whole root store

```php
use Quantum\Config\Config;
use Quantum\Loader\Setup;

$config = new Config();
$config->load(new Setup('config', 'app'));

$name = $config->get('name');
$debug = $config->get('debug', false);
```

Use this pattern for isolated tasks where one file should define the whole config payload.

## Override values at runtime

You can add or replace values after loading.

```php
config()->set('mailer.smtp.host', 'smtp.internal');
config()->set('feature_flags.beta_checkout', true);
```

This updates the in-memory store only. It does not write back to the PHP config file.

## Remove or reset config

```php
config()->delete('feature_flags.beta_checkout');
config()->flush();
```

Use `flush()` carefully. It clears the whole shared store for the current runtime.

## Prefer one loading style per store

Mixing `load()` and `import()` is allowed, but the resulting key shape changes depending on which method populated the store first.

* after `load(new Setup('config', 'app'))`, keys look like `name` and `debug`
* after `import(new Setup('config', 'app'))`, keys look like `app.name` and `app.debug`

Pick one shape deliberately so the rest of your code reads the expected keys.

## Common pitfalls

### Calling `load()` twice

Later `load()` calls are ignored once the store has been initialized.

If you need a fresh root load, call `flush()` first or create a separate `Config` instance.

### Re-importing the same section name

This fails:

```php
config()->import(new Setup('config', 'app'));
config()->import(new Setup('config', 'app')); // throws
```

Use unique filenames per imported section.

### Assuming runtime changes persist to disk

`set()`, `delete()`, and `flush()` change the in-memory copy only.


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