REST APIs

REST (Representational State Transfer) is an architectural style for designing networked applications. RESTful APIs use HTTP methods and are typically simpler than SOAP services.

REST Principles

REST is based on six fundamental constraints:

Client-Server Architecture

Separation of concerns between the user interface (client) and data storage (server).

Stateless

Each request contains all information needed to process it. The server doesn’t store client context between requests.

Cacheable

Responses must define themselves as cacheable or non-cacheable to improve performance.

Uniform Interface

Standardized way of communicating between client and server using HTTP methods.

Layered System

Client cannot tell if it’s connected directly to the server or through intermediaries.

Code on Demand (Optional)

Servers can extend client functionality by transferring executable code.

HTTP Methods

RESTful APIs use HTTP methods to indicate the desired action:

Method	Purpose	Example
GET	Retrieve resource(s)	`GET /api/products`
POST	Create new resource	`POST /api/products`
PUT	Update entire resource	`PUT /api/products/13`
PATCH	Partial update	`PATCH /api/products/13`
DELETE	Remove resource	`DELETE /api/products/13`

REST vs SOAP Comparison

REST Advantages
SOAP Advantages

Simpler: Easier to learn and implement
Flexible formats: JSON, XML, HTML, plain text
Performance: Smaller message size, especially with JSON
Caching: Built-in HTTP caching support
Browser-friendly: Easy to test with browser tools

REST API Design

Resource Naming

Use nouns (not verbs) for resource paths:

✅ Good:
GET  /api/products          # List products
GET  /api/products/13       # Get product 13
POST /api/products          # Create product
PUT  /api/products/13       # Update product 13
DELETE /api/products/13     # Delete product 13

❌ Bad:
GET  /api/getProducts
POST /api/createProduct
POST /api/updateProduct/13
POST /api/deleteProduct/13

HTTP Status Codes

Use appropriate status codes to indicate the result:

Code	Meaning	Usage
200	OK	Successful GET, PUT, PATCH
201	Created	Successful POST
204	No Content	Successful DELETE
400	Bad Request	Invalid request data
401	Unauthorized	Missing or invalid credentials
403	Forbidden	Authenticated but not authorized
404	Not Found	Resource doesn’t exist
500	Server Error	Internal server error

Building a Simple REST API in PHP

Here’s a basic REST API for managing products:

api.php

<?php
header('Content-Type: application/json');

// Get request method and path
$method = $_SERVER['REQUEST_METHOD'];
$path = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
$path = trim($path, '/');
$segments = explode('/', $path);

// Simple routing
if ($segments[0] === 'api' && $segments[1] === 'products') {
    $id = $segments[2] ?? null;
    
    switch ($method) {
        case 'GET':
            if ($id) {
                getProduct($id);
            } else {
                listProducts();
            }
            break;
            
        case 'POST':
            createProduct();
            break;
            
        case 'PUT':
            updateProduct($id);
            break;
            
        case 'DELETE':
            deleteProduct($id);
            break;
            
        default:
            http_response_code(405);
            echo json_encode(['error' => 'Method not allowed']);
    }
} else {
    http_response_code(404);
    echo json_encode(['error' => 'Endpoint not found']);
}

function listProducts() {
    // Database query to get all products
    $products = [
        ['id' => 1, 'nombre' => 'Producto 1', 'pvp' => 19.99],
        ['id' => 2, 'nombre' => 'Producto 2', 'pvp' => 29.99]
    ];
    
    http_response_code(200);
    echo json_encode($products);
}

function getProduct($id) {
    // Database query to get specific product
    if ($id == 1) {
        $product = ['id' => 1, 'nombre' => 'Producto 1', 'pvp' => 19.99];
        http_response_code(200);
        echo json_encode($product);
    } else {
        http_response_code(404);
        echo json_encode(['error' => 'Product not found']);
    }
}

function createProduct() {
    $data = json_decode(file_get_contents('php://input'), true);
    
    if (!isset($data['nombre']) || !isset($data['pvp'])) {
        http_response_code(400);
        echo json_encode(['error' => 'Missing required fields']);
        return;
    }
    
    // Insert into database
    $newId = 3; // Would be from database insert
    
    http_response_code(201);
    echo json_encode([
        'id' => $newId,
        'nombre' => $data['nombre'],
        'pvp' => $data['pvp']
    ]);
}

function updateProduct($id) {
    if (!$id) {
        http_response_code(400);
        echo json_encode(['error' => 'Product ID required']);
        return;
    }
    
    $data = json_decode(file_get_contents('php://input'), true);
    
    // Update in database
    http_response_code(200);
    echo json_encode([
        'id' => $id,
        'nombre' => $data['nombre'],
        'pvp' => $data['pvp']
    ]);
}

function deleteProduct($id) {
    if (!$id) {
        http_response_code(400);
        echo json_encode(['error' => 'Product ID required']);
        return;
    }
    
    // Delete from database
    http_response_code(204);
}

Consuming REST APIs

Using cURL

<?php
// GET request
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://api.example.com/products');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
$products = json_decode($response, true);
curl_close($ch);

// POST request
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://api.example.com/products');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode([
    'nombre' => 'Nuevo Producto',
    'pvp' => 39.99
]));
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
$newProduct = json_decode($response, true);
curl_close($ch);

Using file_get_contents

For simple GET requests:

<?php
$url = 'http://api.example.com/products';
$response = file_get_contents($url);
$products = json_decode($response, true);

foreach ($products as $product) {
    echo $product['nombre'] . ': ' . $product['pvp'] . '€<br>';
}

JSON Format

REST APIs typically use JSON for data exchange:

{
  "id": 13,
  "nombre": "Portátil Dell",
  "familia": "PORTAT",
  "pvp": 899.99,
  "stock": [
    {
      "tienda": 1,
      "unidades": 15
    },
    {
      "tienda": 2,
      "unidades": 8
    }
  ]
}

API Authentication

API Key
Bearer Token
Basic Auth

<?php
$apiKey = 'your-api-key-here';

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://api.example.com/products');
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'X-API-Key: ' . $apiKey
]);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);

<?php
$token = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...';

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://api.example.com/products');
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Authorization: Bearer ' . $token
]);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);

<?php
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://api.example.com/products');
curl_setopt($ch, CURLOPT_USERPWD, 'username:password');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);

Error Handling

<?php
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://api.example.com/products/999');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);

if ($httpCode >= 200 && $httpCode < 300) {
    // Success
    $data = json_decode($response, true);
    echo "Product: " . $data['nombre'];
} elseif ($httpCode == 404) {
    echo "Product not found";
} elseif ($httpCode >= 500) {
    echo "Server error";
} else {
    echo "Request failed with code: $httpCode";
}

Best Practices

Key REST API Best Practices:

Use nouns for resources, not verbs
Use plural names for collections
Use HTTP methods correctly
Return appropriate status codes
Version your API (e.g., /api/v1/products)
Use pagination for large datasets
Implement rate limiting
Provide clear error messages
Use HTTPS in production
Document your API thoroughly

Course Context

In TEMA-06, you’ll compare REST and SOAP approaches, understanding when to use each:

SOAP projects: TAREA-06 implements a product catalog with SOAP services
REST concepts: Applied in API integration in TEMA-08
Hybrid approaches: Some projects may use both patterns

Next Steps

SOAP Introduction

Compare with SOAP web services

API Integration

Learn to consume external APIs

Get Started

PHP Fundamentals

Database Programming

Session Management

Web Services

AJAX & Jaxon

API Integration

Assignments & Exams

REST APIs

REST APIs

REST Principles

HTTP Methods

REST vs SOAP Comparison

REST API Design

Resource Naming

HTTP Status Codes

Building a Simple REST API in PHP

Consuming REST APIs

Using cURL

Using file_get_contents

JSON Format

API Authentication

Error Handling

Best Practices

Course Context

Next Steps

SOAP Introduction

API Integration

Get Started

PHP Fundamentals

Database Programming

Session Management

Web Services

AJAX & Jaxon

API Integration

Assignments & Exams

​REST APIs

​REST Principles

​HTTP Methods

​REST vs SOAP Comparison

​REST API Design

​Resource Naming

​HTTP Status Codes

​Building a Simple REST API in PHP

​Consuming REST APIs

​Using cURL

​Using file_get_contents

​JSON Format

​API Authentication

​Error Handling

​Best Practices

​Course Context

​Next Steps

SOAP Introduction

API Integration

REST APIs

REST Principles

HTTP Methods

REST vs SOAP Comparison

REST API Design

Resource Naming

HTTP Status Codes

Building a Simple REST API in PHP

Consuming REST APIs

Using cURL

Using file_get_contents

JSON Format

API Authentication

Error Handling

Best Practices

Course Context

Next Steps