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Web Sockets in PHP

In his talk Websockets in PHP, John Fransler walks us through the use of WebSockets in PHP.

While discussing bi-directional real-time application development, John notes that PHP is often not invited to the table due to its lack of native support. Of all the possible attempts to bring in PHP on this stage of real-time development, Ratchet, a PHP WebSocket library, comes closest. "Ratchet is a loosely coupled PHP library providing developers with tools to create real-time, bi-directional applications between clients and servers over WebSockets."* Ahem!

Today's dynamic world


In today's dynamic content world of the internet, it is required to serve real-time bi-directional messages between clients and servers. WebSockets are simple, full-duplex, and persistent. They work over Http and are a standard today.

WebSockets have compatibility with 96.5% of clients globally

There's a very high chance your client has the necessary plumbing to access your content via WebSockets. WebSockets gives the ability to have real-time data on to your clients without the need for polling.

To understand WebSockets, John takes an example of a Javascript client and Ratchet Server. Javascript has everything built in to allow access to a socket. For example, you can use the send method on a WebSocket variable to send a message to the server, or if you want to respond to a message from the server, you use the OnConnection method.

While on the Server, John uses Ratchet, which is built on React PHP. A server script is then configured and set up to run and listen on a port for incoming HTTP requests. For messages, JSON is used, and to find public methods, a router is set up. He then goes on to instantiate the server-side script in Ratchet.

There are four functions of a Ratchets message component interface that are used in this example:

OnOpen gets called when a new connection is made.

OnClose gets called when a client quits. It's essential to keep an eye on memory management, and essential to keep tidying up as you move through the code.

OnError gets called when there is an exception faced by the user.

OnMessage gives the text of the JSON message, which is being exchanged with the client.

For Initialization, Jason continues to walk through the example. He shows how one can loop through the clients, both inside the server and outside the server. Outside the server, it’s a feature of React PHP. On database access, and with traditional standard synchronous MySQL in PHP, what usually happens is that it forces the code to wait for the query to return a result and do nothing — Fortunately, with Asynchronous MySQLi, that is not the case.

John gets into the details explaining Variables, References & Pointers. He also gives a demo where a central site has updated information on the Bitcoin and ether prices. A client terminal reflects the last values. Now the client doesn't have to poll the server for new values. When there is a change in the Bitcoin or ether values, the server pushes down the client's update. No polling helps with a lot of overheads and gets closer to real-time.

Using Supervisord


For Long-running applications - Jason recommends running a supervisord, use proxy to expose the port, and add a site certificate. Supervisord keeps an eye out for the server running the service; it can be used to restart the service and log any service issues. Recommended proxies are AWS load balancer, Nginx, and HA Proxy. For scalability, use multiple smaller WebSocket servers and a smaller number of clients per server used and load balancing. If one has to support a chat feature to allow clients to talk to each other in near real-time, it is recommended to use Redis. The Redis server proxies the messages between the server nodes.

The talk concludes with John summarizing best practices on error handling and takes QnA on various aspects of WebSockets such as handling load balancers and asynchronous calls to MSQLi.

The presentation for this video, along with the code, is hosted at John Curt's GitHub. More info about John's current areas of interest can be found on John's Blog.

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