HTTP Protocol

HTTP stands for HyperText Transfer Protocol.

HTTP defines how messages are exchanged between clients and servers over a network.

Client
  ↓
HTTP Request
  ↓
Server
  ↓
HTTP Response
  ↓
Client

HTTP is important for REST API development because it provides the communication mechanism between the client and server.

A React Native application can use HTTP requests to communicate with a PHP REST API.

HTTP communication normally involves a client and a server.

React Native
     ↓
HTTP Request
     ↓
PHP REST API
     ↓
HTTP Response
     ↓
React Native

The client starts the communication by sending a request.

An HTTP request is a message sent from the client to the server.

For example:

GET /api/students

This request can ask the server to return student information.

An HTTP response is a message sent from the server back to the client.

For example:

HTTP/1.1 200 OK

{
    "success": true,
    "message": "Students found"
}

An HTTP request can contain several important components.

• Request method
• Request URL
• Request headers
• Query parameters
• Request body

The exact parts used depend on the request.

An HTTP response can contain:

• Status code
• Response headers
• Response body

Status Code
     ↓
Headers
     ↓
Response Body

HTTP provides methods that describe the intended operation of a request.

GET is commonly used when the client wants to retrieve information.

GET /api/students

The server can process the request and return a list of students.

POST is commonly used to send data to the server.

POST /api/students

The request can contain student information in the request body.

PUT is commonly used to update an existing resource.

PUT /api/students/10

The server can use the ID to identify the resource that needs to be updated.

PATCH is commonly used to partially update an existing resource.

PATCH /api/students/10

For example, only the student's email address may need to be changed.

DELETE is commonly used to remove a resource.

DELETE /api/students/10

The server can process the request and remove the corresponding record.

A URL identifies the location of a resource or API endpoint.

Example:

https://example.com/api/students

The client sends its HTTP request to this URL.

HTTP and HTTPS are both used for web communication.

HTTPS is HTTP communication protected using encryption through TLS.

For production applications, HTTPS should be used to protect data during network communication.

HTTP headers provide additional information about a request or response.

Example request header:

Content-Type: application/json

Headers can also carry authentication information.

The Content-Type header tells the server what type of data is being sent in the request body.

For JSON:

Content-Type: application/json

This is commonly used when React Native sends JSON data to a REST API.

The Accept header can indicate the type of response the client expects from the server.

Example:

Accept: application/json

This tells the server that the client expects JSON data.

HTTP status codes tell the client what happened while processing the request.

• 2xx – Successful requests
• 3xx – Redirection
• 4xx – Client-side errors
• 5xx – Server-side errors

A POST request can send JSON data to a REST API.

POST /api/students
Content-Type: application/json

{
    "name": "Rahul",
    "email": "rahul@example.com",
    "course": "React Native"
}

The PHP API can read this JSON and process the data.

The server can return JSON in the response body.

HTTP/1.1 200 OK
Content-Type: application/json

{
    "success": true,
    "message": "Student found",
    "data": {
        "id": 10,
        "name": "Rahul"
    }
}

React Native can send an HTTP request using the Fetch API.

fetch("https://example.com/api/students")
    .then(response => response.json())
    .then(data => {
        console.log(data);
    });

The response is converted to JSON and can then be used by the application.

A POST request can send JSON data to the server.

fetch("https://example.com/api/students", {
    method: "POST",
    headers: {
        "Content-Type": "application/json"
    },
    body: JSON.stringify({
        name: "Amit",
        email: "amit@example.com"
    })
});

Authentication information can be included in HTTP headers.

For token-based authentication:

Authorization: Bearer YOUR_TOKEN

The PHP REST API can verify the token before processing a protected request.

The mobile application should check the response and handle errors.

For example:

if (!response.ok) {
    console.log("API request failed");
}

The application can then display a suitable error message.

React Native
      ↓
HTTP Request
      ↓
HTTPS / Internet
      ↓
PHP REST API
      ↓
MySQL
      ↓
PHP REST API
      ↓
HTTP Response
      ↓
React Native

This communication pattern is used throughout our REST API and mobile application projects.

Before continuing with REST API development, remember these HTTP concepts:

• Request
• Response
• HTTP method
• URL
• Headers
• Request body
• Response body
• Status code
• HTTP and HTTPS

HTTP will be used throughout this course.

React Native
      ↓
HTTP / HTTPS
      ↓
PHP REST API
      ↓
MySQL

The upcoming lessons will use HTTP methods, headers, JSON, status codes, and API endpoints to build complete backend services.

The most important concept is the HTTP request-response cycle.

                CLIENT
          React Native App
                  ↓
            HTTP Request
                  ↓
        ┌─────────────────┐
        │   REST API      │
        │   PHP Backend   │
        └────────┬────────┘
                 ↓
              MySQL
                 ↓
        ┌─────────────────┐
        │   REST API      │
        │   PHP Backend   │
        └────────┬────────┘
                 ↓
           HTTP Response
                 ↓
          React Native App

Once you understand HTTP, you can understand how REST APIs communicate with React Native applications.