1. Introduction
JSON Web Tokens (JWT) is an open standard for securely transmitting information between parties as a JSON object. It is commonly used for authentication and authorization in web applications. PHP provides libraries and functions to easily implement JWT in web applications. In this tutorial, we will go through the steps of using JWT in a web application using PHP.
2. Installing Required Libraries
2.1. JSON Web Token Library
To start using JWT in PHP, we need to install a library that provides the required functionality. One popular library is "firebase/php-jwt". Use Composer, the dependency manager for PHP, to easily install the library.
composer require firebase/php-jwt
2.2. JSON Web Token Library for PHP
The library "firebase/php-jwt" provides a PHP implementation of JWT. It includes functions for creating JWT tokens, verifying tokens, and extracting the payload from a token.
use \Firebase\JWT\JWT;
3. Generating a JWT Token
To generate a JWT token, we need to create a payload and sign it with a secret key. The payload can contain any data that needs to be transmitted securely. For example, we can include the user ID and expiration time in the payload.
$payload = [
"user_id" => 123,
"exp" => time() + 3600
];
$jwt = JWT::encode($payload, "secret_key");
In the above code, we create a payload array with the user ID and expiration time. We then use the "JWT::encode()" function to encode the payload and generate the JWT token. The second parameter is the secret key used for signing the token.
4. Verifying a JWT Token
To verify a JWT token, we need to decode it and verify its signature using the secret key. If the token is valid and not expired, we can extract the information from the payload.
$jwt = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjoxMjMsImV4cCI6MTYxMzIxMDQwMH0.EPyJCyhfpgEm8KE5QsgzB7LKo3N-PxGh2wWUpNS6wN8";
try {
$decoded = JWT::decode($jwt, "secret_key", array('HS256'));
$user_id = $decoded->user_id;
} catch (Exception $e) {
echo "Invalid token: " . $e->getMessage();
}
In the above code, we decode the JWT token using the "JWT::decode()" function. We pass the token, secret key, and the algorithm used for signing the token. If the token is valid, its signature is verified and the payload is decoded. We can then access the user ID from the decoded payload.
5. Using JWT in Web Applications
JWT can be used in various scenarios in web applications, such as authentication and API access control.
5.1. Authentication
JWT can be used for user authentication in web applications. When a user logs in, a JWT token can be generated and sent back to the client. The client can then include the token in subsequent requests to authenticate the user without sending the username and password with each request.
5.2. API Access Control
JWT can be used to control access to APIs in web applications. When a client requests an API, it needs to include a JWT token in the request headers. The server can then verify the token and determine if the client has the necessary permissions to access the requested API.
6. Conclusion
In this tutorial, we have learned how to use JWT in web applications using PHP. We have covered the steps of generating a JWT token, verifying a JWT token, and using JWT for authentication and API access control. JWT provides a secure and efficient way to transmit information between parties in a web application.