Getting Started with PHP: JWT Tokens

As modern web applications continue to evolve, authentication and security are becoming increasingly important. One of the popular methods is to use JWT (JSON Web Tokens) tokens for authentication. This article will introduce you to the basics and techniques of implementing JWT tokens using PHP.

1. JWT Token Overview

JWT is an open standard that defines a way to securely and efficiently transmit claims by transmitting JSON objects over the network. JWT consists of three parts: header, payload and signature. The header contains the type of token and the hash algorithm used, the payload contains authentication and authorization information, and the signature is a string combining the header and payload hashes and key.

JWT supports stateless, server-side authentication, avoiding the need to use server sessions or cookies. And it's easy to extend because it's a standardized JSON format.

2. PHP implementation process

The PHP language provides many classes that can easily generate and verify JWT tags. Creating JWT in PHP requires the use of a library, we use the php-jwt library, which is available for free on GitHub.

Install the php-jwt library:
composer require firebase/php-jwt

Creating a JWT token is simple, here is the sample code:

require_once('vendor/autoload.php');
use FirebaseJWTJWT;

$key = "example_key";
$payload = array(
    "iss" => "http://example.org",
    "aud" => "http://example.com",
    "iat" => 1356999524,
    "nbf" => 1357000000
);

$jwt = JWT::encode($payload, $key);
print_r($jwt);

In this example , we use a key example_key and some clues, such as the issuer of the token iss, and the recipients who can use the token aud . We also define the life cycle of the JWT, that is, it should be usable after the token issuance time iat and before the current time point nbf.

The final result of JWT is a long string in the form of AAA.BBB.CCC. AAA is the header, BBB is the payload, and CCC is the signature, which is generated by the key.

Verification of the JWT token requires the use of the same key, the sample code is as follows:

require_once('vendor/autoload.php');
use FirebaseJWTJWT;

$key = "example_key";
$jwt = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJhdWQiOiJodHRwOi8vZXhhbXBsZS5jb20iLCJpYXQiOjEzNTY5OTk1MjQsIm5iZiI6MTM1NzAwMDAwMCwiZXhwIjoxMzU3MDAwMDAwfQ.kn4N5lvvvdQhL7rEixJOaYWKQZ3GzrCc8REIzc2Kw8c";

$decoded = JWT::decode($jwt, $key, array('HS256'));

print_r($decoded);

If the token can be successfully decoded, then your code will output the same associative array as in the payload. If authentication fails, an exception will be thrown.

3. Conclusion

This article explains how to implement JWT tokens using PHP. JWT is a simple but useful tool that can make your applications more secure and avoid using traditional session mechanisms. We hope this article helped you better understand JWT and how to use it in PHP applications.

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