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README.md

OpenTok Hello World PHP

This is a simple demo app that shows how you can use the OpenTok-PHP-SDK to create Sessions, generate Tokens with those Sessions, and then pass these values to a JavaScript client that can connect and conduct a group chat.

Running the App

First, download the dependencies using Composer in this directory.

$ ../../composer.phar install

Next, input your own API Key and API Secret into the run-demo script file:

  export API_KEY=0000000
  export API_SECRET=abcdef1234567890abcdef01234567890abcdef

Finally, start the PHP CLI development server (requires PHP >= 5.4) using the run-demo script

$ ./run-demo

Visit http://localhost:8080 in your browser. Open it again in a second window. Smile! You've just set up a group chat.

Walkthrough

This demo application uses the Slim PHP micro-framework and a lightweight caching library. These are similar to many other popular web frameworks and data caching/storage software. These concepts won't be explained but can be explore further at each of the websites linked above.

Main Controller (web/index.php)

The first thing done in this file is to require the autoloader which pulls in all the dependencies that were installed by Composer. We now have the Slim framework, the Cache library, and most importantly the OpenTok SDK available.

require($autoloader);

use Slim\Slim;
use Gregwar\Cache\Cache;

use OpenTok\OpenTok;

Next the controller performs some basic checks on the environment, initializes the Slim application ($app), and sets up the cache to be stored in the application's container ($app->cache).

The first thing that we do with OpenTok is to initialize an instance and also store it in the application container. At the same time, we also store the apiKey separately so that we can access it on its own. Notice that we needed to get the API_KEY and API_SECRET from the environment variables.

// Initialize OpenTok instance, store it in the app contianer
$app->container->singleton('opentok', function () {
    return new OpenTok(getenv('API_KEY'), getenv('API_SECRET'));
});
// Store the API Key in the app container
$app->apiKey = getenv('API_KEY');

Now we are ready to configure some routes. We only need one GET route for the root path because this application only has one page. Inside the route handler, we query the cache to see if we have stored a sessionId previously. The reason we use a cache in this application is because we want to generate a session only once, no matter how many times the page is loaded, so that all visitors can join the same OpenTok Session. In other applications, it would be common to save the sessionId in a database table. If the cache does not have a sessionId stored, like on the first run of the application, we use the stored OpenTok instance to create a Session. When we return its sessionId, that will be stored in the cache for later use.

NOTE: in order to clear the cache, just delete the cache folder created in your demo app directory.

// If a sessionId has already been created, retrieve it from the cache
$sessionId = $app->cache->getOrCreate('sessionId', array(), function () use ($app) {
    // If the sessionId hasn't been created, create it now and store it
    $session = $app->opentok->createSession();
    return $session->getSessionId();
});

Next inside the route handler, we generate a Token, so the client has permission to connect to that Session. This is again done by accessing the stored OpenTok instance. Since the token is not cached, a fresh one is generated each time.

// Generate a fresh token for this client
$token = $app->opentok->generateToken($sessionId);

Lastly, we load a template called helloworld.php in the templates/ directory, and pass in the three values needed for a client to connect to a Session: apiKey, sessionId, and token.

$app->render('helloworld.php', array(
    'apiKey' => $app->apiKey,
    'sessionId' => $sessionId,
    'token' => $token
));

Main Template (templates/helloworld.php)

This file simply sets up the HTML page for the JavaScript application to run, imports the JavaScript library, and passes the values created by the server into the JavaScript application inside web/js/helloworld.js

JavaScript Application (web/js/helloworld.js)

The group chat is mostly implemented in this file. At a high level, we connect to the given Session, publish a stream from our webcam, and listen for new streams from other clients to subscribe to.

For more details, read the comments in the file or go to the JavaScript Client Library for a full reference.

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