# Request Lifecycle for a Mezzio-Based Application

## Summary

The eleven steps a Dotkernel Light request travels through, from `public/index.php` to the emitted response.

## Details

The request lifecycle is the sequence of steps that happen from the moment a user makes an HTTP request until the server sends back a response.

The graph below shows how the request is handled by Dotkernel Light.

![Dotkernel Light Request Lifecycle!](https://docs.dotkernel.org/img/light/request-lifecycle.jpg)

## Request Lifecycle Step-by-Step

The following list describes what each of the steps from the graph does in Dotkernel Light.

### 1. HTTP Request [public/index.php]

- Bootstrap the application.
- Load configuration.
- Create the Mezzio application instance.

### 2. Service Container

Register:

- Factories.
- Aliases.
- Delegators.

All services are configured and ready to use.

### 3. Route Registration

Read all available routes with their allowed request methods and dynamically register them in the application.
Routes are managed by FastRoute.

#### Example

| Item       | Value                             |
|------------|-----------------------------------|
| Match      | /page/about -> GetPageViewHandler |
| Method     | GET                               |
| Route name | page::about                       |

### 4. Middleware Pipeline [config/pipeline.php]

Loads the predefined order of middleware.
It defines how incoming HTTP requests move through the application and how responses are generated.

### 5. Routing

FastRoute matches the URL and method against registered routes.

#### Example

| Item       | Value              |
|------------|--------------------|
| Match      | GET /page/about    |
| Handler    | GetPageViewHandler |
| Route name | page::about        |

### 6. Handler Invocation

Extract the matched route name from the request and pass it to the renderer.

```php
$template = $request->getAttribute(RouteResult::class)->getMatchedRouteName();
// $template = 'page::about';
```

### 7. Custom Logic Execution in Handler

Execute the business logic in the handler.
The process can involve services and any custom logic.

### 8. Template Rendering

Twig loads the template, applies layout, renders blocks and includes partials.

#### Example

| Item             | Value                                   |
|------------------|-----------------------------------------|
| Load             | src/Page/templates/page/about.html.twig |
| Extends          | @layout/default.html.twig               |
| Render blocks    | title, content                          |
| Include partials | alerts.html.twig, etc.                  |
| Output           | Final HTML                              |

### 9. Response Creation

An HtmlResponse is created with status, headers and the rendered HTML body.

#### Example

| Item         | Value                    |
|--------------|--------------------------|
| Status       | 200 OK                   |
| Content-Type | text/html; charset=utf-8 |
| Body         | Rendered HTML            |

### 10. Response Pipeline

The response flows back through the middleware stack.
Middleware can modify headers, cookies, compress content, etc.

### 11. Response Emitter

The final response is sent back to the browser.
The page is rendered and sent to the user.

## FAQ

**Q: How many steps does a Dotkernel Light request go through?**
A: Eleven, from the initial HTTP request in `public/index.php` to the response emitter.

**Q: Which component matches the URL to a handler?**
A: FastRoute, in the routing step.

**Q: How does a handler know which template to render?**
A: It reads the matched route name off the request, for example `page::about`, and passes it to the Twig renderer.