The Connected Web

Modern websites and applications rarely live in isolation. Think about the weather app on your phone—it doesn't have its own weather station. Instead, it "talks" to a weather service to get the latest forecast. When you see a Google Map embedded on a website, that website is "talking" to Google's mapping service. This communication between different applications is made possible by APIs.

What is an API? The Restaurant Analogy

API stands for Application Programming Interface. In simple terms, an API is a set of rules and tools that allows different software applications to communicate with each other. It's an intermediary that handles requests and responses.

The best way to understand it is with the restaurant analogy:

  • You (the Client) are a customer sitting at a table. You want food.
  • The kitchen (the Server) has all the ingredients and data needed to prepare your food.
  • You cannot go directly into the kitchen to get what you want. You need an intermediary.
  • The API is the Waiter.

The waiter provides you with a Menu (the API documentation) that tells you what you can order. You give the waiter a structured request ("I'd like the steak, medium-rare"). The waiter takes your request to the kitchen, the kitchen prepares your order, and the waiter brings the food back to you on a plate in a predictable format. You don't need to know how the kitchen works; you only need to know how to talk to the waiter.

Key API Concepts

When working with APIs, you'll encounter these terms frequently:

  • Endpoint: A specific URL where an API can be accessed. It's like a specific item on the restaurant menu. For example, https://api.example.com/users/123 is an endpoint to get information about user 123.
  • HTTP Methods (Verbs): The action you want to perform. The most common are:
    • GET: Retrieve data (e.g., get a user's profile).
    • POST: Submit new data (e.g., create a new user).
    • PUT / PATCH: Update existing data.
    • DELETE: Remove data.
  • Request & Response: The communication cycle. Your application sends a Request to an endpoint, and the server sends back a Response.
  • JSON (JavaScript Object Notation): This is the most common data format for modern APIs. It's a lightweight, human-readable text format that is easy for machines to parse. It's the "language" the waiter uses to write down your order and the kitchen uses to list the ingredients.

Here's an example of a user's data represented in JSON:


{
  "id": 123,
  "name": "John Doe",
  "email": "john.doe@example.com",
  "isActive": true
}

What is a REST API?

REST (Representational State Transfer) is an architectural style, or a set of popular conventions, for building APIs. It's not a strict protocol, but a guide. Most public APIs you will use are REST APIs. They typically use:

  • Standard HTTP methods (GET, POST, etc.).
  • URLs that are structured around "resources" (e.g., /users, /posts, /products).
  • JSON as the primary data format.

In the next lesson, we will use PHP to consume a real-world REST API and fetch live data.