Welcome to the next step in our journey of building a personal tutor service with Symfony. In the previous lesson, we focused on the TutorController, which manages tutoring sessions and handles student queries by interacting with both the model and service layers. Now, we will take a significant step forward by creating a RESTful API for our personal tutor service using Symfony. We'll explore how to structure our application with an ApiController that serves as the entry point for HTTP requests and delegates business logic to the TutorController.

RESTful APIs are a way for different software systems to communicate over the internet. They provide a set of rules that allow programs to exchange data. Symfony is a popular PHP framework that simplifies the process of building web applications, including RESTful APIs. It offers a clean and flexible architecture, making it easy to create robust and scalable applications.

Symfony's routing system, controller architecture, and HTTP foundation components make it an excellent choice for building RESTful APIs. These components allow us to define clear endpoints, process requests, and return structured responses.

In our personal tutor service, we're implementing a two-controller architecture:

1. ApiController: Acts as the entry point for all HTTP requests, handling routing, request parsing, and response formatting
2. TutorController: Contains the business logic for managing tutoring sessions and processing student queries

This separation of concerns allows us to keep our API interface clean and focused on HTTP interactions, while the core tutoring logic remains independent of the web layer.

The ApiController serves as the entry point for all HTTP requests to our API. It's responsible for:

• Defining routes using Symfony's annotation system
• Parsing incoming request data
• Delegating to the TutorController for business logic
• Formatting responses as JSON

Let's examine the key components of our ApiController:

Notice how each method in the ApiController follows a similar pattern:

The TutorController contains the core business logic for our personal tutor service. It's responsible for:

• Managing student sessions
• Processing student queries
• Interacting with the TutorService to generate responses

Let's examine the key components of our TutorController:

The TutorController handles several key responsibilities:

While Symfony supports route definitions using PHP attributes (annotations) directly in your controller classes, you can also define your application's routes in a configuration file called routes.yaml. This approach is especially useful for centralizing and managing your routes in one place.

Here's an example of how you can define the home page route in config/routes.yaml:

In this example:

• app_index is the name of the route.
• path specifies the URL path (/ for the home page).
• controller points to the controller and method that should handle the request.

You can define additional routes for your API endpoints in the same file:

This approach provides a clear overview of all your application's routes and can be used alongside or instead of PHP attribute-based routing, depending on your project's needs.

Our application uses Symfony's session management to track student interactions. The SessionInterface is automatically injected into our controller methods, allowing us to:

• Generate and store unique student IDs
• Maintain state between requests
• Ensure security by validating session data

The ensureUserSession method demonstrates this pattern:

This method checks if a student ID exists in the session, creates one if needed, and returns the ID. This ensures that each student has a consistent identity across multiple requests.

Our API implements consistent error handling and response formatting. The TutorController returns structured arrays that include:

• Success responses with relevant data
• Error responses with descriptive messages and appropriate HTTP status codes

The ApiController then converts these structured arrays into proper HTTP responses using Symfony's JsonResponse class:

This approach ensures that our API provides clear, consistent responses that clients can easily parse and handle.

To run your Symfony application, you can use the built-in web server provided by the Symfony CLI:

Or, if you don't have the Symfony CLI:

This command will start the Symfony development server, making your application accessible at http://localhost:3000. You can now test your API endpoints using a tool like Postman or a web browser.

Our personal tutor service exposes three main endpoints:

1. GET / - The home page that welcomes users and ensures they have a session
2. POST /api/create_session - Creates a new tutoring session for the current student
3. POST /api/send_query - Processes a student query and returns a tutor response

To use the API, clients would typically:

1. Visit the home page to establish a session
2. Create a tutoring session using the /api/create_session endpoint
3. Send queries using the /api/send_query endpoint, including the session ID and query text

In this lesson, we successfully built a RESTful API for our personal tutor service using Symfony. We implemented a two-controller architecture that separates HTTP concerns from business logic, used Symfony's session management to track student interactions, and created a consistent error handling and response formatting system.

This architecture provides a solid foundation for our personal tutor service, allowing it to scale and evolve as we add more features. The separation of concerns between the ApiController and TutorController makes our code more maintainable and testable, while Symfony's powerful features handle the complexities of HTTP interactions and session management.

As you move on to the practice exercises, take the opportunity to experiment with the Symfony API and reinforce the concepts covered in this lesson. Try adding new endpoints, enhancing error handling, or extending the session management system to better understand how these components work together.