> 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/advanced-features/environment.md).

# Environment

The Quantum PHP Framework uses an environment-based configuration system to manage settings for different stages of the application lifecycle (e.g., development, production, testing).

## File Selection

The framework selects the environment file based on the `app_env` setting, which is determined during the initial loading phase.

* **Production**: Uses `.env`.
* **Other environments**: Uses `.env.{app_env}` (e.g., `.env.development`, `.env.staging`).

## Lifecycle and Loading

The `Environment` service implements a "one-shot" loading pattern.

### `load(Setup $setup)`

* **One-shot**: Once the environment is loaded, subsequent calls to `load()` are no-ops.
* **Initialization**: It identifies the target `.env` file, validates its existence, loads the variables, and marks the environment as loaded.

### `env(string $key, $default = null)`

This helper function provides access to environment variables.

* **Contract**: You must call `load()` before accessing any variables via `env()`. If the environment has not been loaded yet, calling `env()` will throw an `EnvException`.

> **Warning**: In long-lived processes (like workers, daemons, or some test suites), be aware that once `load()` is executed, the environment state is fixed. Reloading variables requires the process or the service state to be reset.

## Server Accessor Contract

The `Server` class provides a controlled gateway to the server state.

### Metadata Accessor Details

| Method              | Behavior Contract                                                                                                                          |
| ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| `protocol()`        | Returns `https` if `HTTPS` is truthy/not `off` OR `SERVER_PORT` is `443`; defaults to `http`.                                              |
| `contentType(true)` | Returns `CONTENT_TYPE` but strips all characters after the first `;` (e.g., `application/json; charset=UTF-8` becomes `application/json`). |
| `getAllHeaders()`   | Normalizes `HTTP_*` keys by removing the prefix, converting underscores to hyphens, and forcing lowercase.                                 |
| `acceptedLang()`    | Extracts the first language from `HTTP_ACCEPT_LANGUAGE` and returns only the first two characters in lowercase.                            |
| `ip()`              | Precedence: `HTTP_CLIENT_IP` -> `HTTP_X_FORWARDED_FOR` -> `REMOTE_ADDR`.                                                                   |

> **Proxy/Security Caveat**: The `ip()` method trusts headers provided by the client (proxies/load balancers). In production environments, ensure your entry point configures the application to support only trusted proxies.

```php
$setup = new Setup('config', 'env', true, 'php');

$env = Di::get(Environment::class);
$env->load($setup);

// Access a variable
$dbHost = env('DB_HOST', 'localhost');
```

## What to read next

After environment loading behavior, continue with:

* [Configuration](/docs/advanced-features/configuration.md)
* [Request Lifecycle](/docs/advanced-features/request-lifecycle.md)
* [Modules](/docs/core-concepts/modules.md)


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