Lesson 17: PHP and APIs

APIs (Application Programming Interfaces) allow systems to communicate with each other. RESTful APIs are widely used in web applications to exchange data. In this lesson, you will learn how to consume RESTful APIs and build a simple REST API using PHP.

Lesson Outline

1. Introduction to RESTful APIs
2. Consuming RESTful APIs
3. Building a Simple REST API with PHP

17.1 Introduction to RESTful APIs

What is a RESTful API?

• REST (Representational State Transfer) is an architectural style for designing APIs.
• Key Features:
  • Stateless: Each request is independent and contains all necessary information.
  • HTTP Methods: Standard HTTP methods are used for CRUD operations:
    • GET: Retrieve data.
    • POST: Create data.
    • PUT: Update data.
    • DELETE: Delete data.
  • Resource-based: Data is represented as resources (e.g., /users, /products).

17.2 Consuming RESTful APIs

Fetching Data with file_get_contents

Example: Fetching Data from a Public API

Using cURL to Consume APIs

What is cURL?

• cURL is a library in PHP for making HTTP requests.

GET Request with cURL

POST Request with cURL

17.3 Building a Simple REST API with PHP

Setting Up the Environment

1. Create a new database api_demo and a table users:
   sql

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   CREATE DATABASE api_demo;

   USE api_demo;

   CREATE TABLE users (
   id INT AUTO_INCREMENT PRIMARY KEY,
   name VARCHAR(100),
   email VARCHAR(100),
   created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
   );

2. Insert sample data:
   sql

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   INSERT INTO users (name, email) VALUES
('Alice', 'alice@example.com'),
('Bob', 'bob@example.com');

3. Create a file db.php for database connection:
   php

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   <?php
$host = "localhost";
$username = "root";
$password = "";
$database = "api_demo";try {
   $conn = new PDO(“mysql:host=$host;dbname=$database“, $username, $password);
   $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
   } catch (PDOException $e) {
   die(“Connection failed: “ . $e->getMessage());
   }
   ?>

Creating the REST API

Step 1: API Endpoint Structure

• /api/users – GET (Retrieve all users)
• /api/users/:id – GET (Retrieve a specific user)
• /api/users – POST (Create a new user)
• /api/users/:id – PUT (Update a user)
• /api/users/:id – DELETE (Delete a user)

Step 2: Base API File (api.php)

Step 3: Handle GET Requests

Step 4: Handle POST Requests

Step 5: Handle PUT Requests

Step 6: Handle DELETE Requests

Testing the API

1. Use tools like Postman or cURL to test API endpoints.
2. Example cURL commands:
   • GET all users:
     bash

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     curl -X GET http://localhost/api/users

   • POST a new user:
     bash

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     curl -X POST -H "Content-Type: application/json" -d '{"name":"Charlie","email":"charlie@example.com"}' http://localhost/api/users


Activities and Exercises

1. Consuming APIs:
   • Fetch and display posts from the JSONPlaceholder API using cURL.
2. Building APIs:
   • Extend the users API to include user authentication (e.g., login).
3. Validation:
   • Add validation for user input (e.g., email format, required fields) in the POST and PUT endpoints.

Assignment

1. Create a database library with tables:
   • books: id, title, author.
   • users: id, name, email.
   • borrowed_books: id, user_id, book_id, borrowed_at.
2. Build an API with the following endpoints:
   • /api/books (GET): Retrieve all books.
   • /api/users/:id/borrowed (GET): Retrieve books borrowed by a user.
   • /api/borrow (POST): Borrow a book.