PHP

Let's create a sample application that authenticates a user with a PHP application. We'll take a simple approach here, appropriate for the written format. Still, you should check out the accompanying Quickstart app on GitHub for a more robust example.

The Auth0 PHP SDK supports many PHP-FIG standards offering interoperability options with your architecture. Two of particular importance are PSR-17 and PSR-18. These standards allow you to plug-in networking components of your choice to handle messaging and requests. You will need to install compatible libraries in your project for the SDK to use.

The most prolific networking library for PHP is Guzzle, although many are available to pick from within the PHP community. Let's use Guzzle for this sample application. Once again, from your project directory, run the following shell command:

composer require guzzlehttp/guzzle guzzlehttp/psr7 http-interop/http-factory-guzzle

composer require auth0/auth0-php

To begin, let's create a .env file within the root of your project directory to store our sample application's configuration and fill in the environment variables:

# Your Auth0 application's Client ID
AUTH0_CLIENT_ID=YOUR_CLIENT_ID

# The URL of your Auth0 tenant domain
AUTH0_DOMAIN=YOUR_DOMAIN

# Your Auth0 application's Client Secret
AUTH0_CLIENT_SECRET=YOUR_CLIENT_SECRET

# A long, secret value used to encrypt the session cookie.
# This can be generated using `openssl rand -hex 32` from your shell.
AUTH0_COOKIE_SECRET=

# A url your application is accessible from. Update this as appropriate.
AUTH0_BASE_URL=http://127.0.0.1:3000

As PHP isn't able to read our .env file by itself, we'll want to install a library to help with that. Although we'll be using a particular library for our sample application's purposes, in a real world application any 'dotenv' loader of preference will work. From our project directory, let's run the following shell command to install the library:

composer require vlucas/phpdotenv

Next, let's create the PHP source file we'll be using for these code samples, index.php, and let's configure an instance of the Auth0 PHP SDK for our sample application:

<?php

// Import the Composer Autoloader to make the SDK classes accessible:
require 'vendor/autoload.php';

// Load our environment variables from the .env file:
(Dotenv\Dotenv::createImmutable(__DIR__))->load();

// Now instantiate the Auth0 class with our configuration:
$auth0 = new \Auth0\SDK\Auth0([
    'domain' => $_ENV['AUTH0_DOMAIN'],
    'clientId' => $_ENV['AUTH0_CLIENT_ID'],
    'clientSecret' => $_ENV['AUTH0_CLIENT_SECRET'],
    'cookieSecret' => $_ENV['AUTH0_COOKIE_SECRET']
]);

Modern PHP applications use a routing pattern to pass incoming HTTP requests to the code that handles them, determining what should happen when our users visit a particular "page" in our app. There is no single, correct way of implementing routing in your application, and there are many libraries to choose from to implement it. We'll be using one particular library for our sample application's purposes, but feel free to select your own in a real-world application.

From our project directory, let's run the following shell command to install the routing library:

composer require steampixel/simple-php-router

Next, let's open our index.php back up and give our application life. Start by importing the routing library and defining our sample application's route's full URLs as named constants for convenience sake, as we'll need to reference them in a few places through our sample application:

// 👆 We're continuing from the steps above. Append this to your index.php file.

// Import our router library:
use Steampixel\Route;

// Define route constants:
define('ROUTE_URL_INDEX', rtrim($_ENV['AUTH0_BASE_URL'], '/'));
define('ROUTE_URL_LOGIN', ROUTE_URL_INDEX . '/login');
define('ROUTE_URL_CALLBACK', ROUTE_URL_INDEX . '/callback');
define('ROUTE_URL_LOGOUT', ROUTE_URL_INDEX . '/logout');

Now we can move on to adding our application's route handling logic, and the SDK integrations:

The Auth0 PHP SDK has a convenient method for checking if our user has authenticated and returned their profile, getCredentials(). Let's install this on our index route to print the user profile if they're logged in or report that they need to login.

// 👆 We're continuing from the steps above. Append this to your index.php file.

Route::add('/', function() use ($auth0) {
  $session = $auth0->getCredentials();

  if ($session === null) {
    // The user isn't logged in.
    echo '<p>Please <a href="/login">log in</a>.</p>';
    return;
  }

  // The user is logged in.
  echo '<pre>';
  print_r($session->user);
  echo '</pre>';

  echo '<p>You can now <a href="/logout">log out</a>.</p>';
});

We can access all the properties of our user's profile from the user property response, which is an array. So, for example, we can pull the user's nickname using $session->user['nickname'], or their email address from $session->user['email']. The structure is a normalized user profile, which you can learn more about here.

It's important to note that the content of the user profile will vary depending on the social provider(s) you use, so you should never assume that a particular value will always be there within your application logic. Use PHP language constructs like isset or null coalescence to gracefully handle a value's presence, or lack thereof, for example:

// ✋ We don't need to include this in our sample application, it's just an example.
$name = $session->user['name'] ?? $session->user['nickname'] ?? $session->user['email'] ?? 'Unknown';

Now let's create our /login route, which will use the Auth0 PHP SDK's login() method to set up the user session and return a customized URL to Auth0's Universal Login Page for this user to login.

// 👆 We're continuing from the steps above. Append this to your index.php file.

Route::add('/login', function() use ($auth0) {
    // It's a good idea to reset user sessions each time they go to login to avoid "invalid state" errors, should they hit network issues or other problems that interrupt a previous login process:
    $auth0->clear();

    // Finally, set up the local application session, and redirect the user to the Auth0 Universal Login Page to authenticate.
    header("Location: " . $auth0->login(ROUTE_URL_CALLBACK));
    exit;
});

After our users return from authenticating with the Auth0's Universal Login Page, they'll return to our sample application at our callback route, /callback which we'll handle in this step.

When Auth0 passes our users back to us, it includes a few essential parameters in the query of the HTTP request. The Auth0 PHP SDK's exchange() method handles working with those, so finishing our authentication flow is straightforward:

// 👆 We're continuing from the steps above. Append this to your index.php file.

Route::add('/callback', function() use ($auth0) {
    // Have the SDK complete the authentication flow:
    $auth0->exchange(ROUTE_URL_CALLBACK);

    // Finally, redirect our end user back to the / index route, to display their user profile:
    header("Location: " . ROUTE_URL_INDEX);
    exit;
});

Last but not least, let's properly handle logging our users out. The logout() method of the Auth0 PHP SDK handles clearing our sample application's session cookies, redirecting the user to Auth0's /logout endpoint (which logs out Auth0 session layer and any identify provider session layers), and then return the user to our / index route.

// 👆 We're continuing from the steps above. Append this to your index.php file.

Route::add('/logout', function() use ($auth0) {
    // Clear the user's local session with our app, then redirect them to the Auth0 logout endpoint to clear their Auth0 session.
    header("Location: " . $auth0->logout(ROUTE_URL_INDEX));
    exit;
});

Last but not least, we need to tell our routing middleware to actually route requests:

// 👆 We're continuing from the steps above. Append this to your index.php file.

// This tells our router that we've finished configuring our routes, and we're ready to begin routing incoming HTTP requests:
Route::run('/');

That's it! You're ready to run your new application; once again, from your project directory, run the following shell command:

php -S 127.0.0.1:3000 index.php

Open your browser to http://127.0.0.1:3000 and try it out.