I have tried reading some articles, but I am not very clear on the concepts yet.
Would someone like to take a shot at explaining to me what these technologies are:
- Long Polling
- Server-Sent Events
One thing that I came across every time was, the server keeps a connection open and pushes data to the client. How is the connection kept open, and how does the client get the pushed data? (How does the client use the data, maybe some code might help?)
Now, which one of them should I use for a real-time app. I have been hearing a lot about websockets (with socket.io [a node.js library]) but why not PHP?
In the examples below the client is the browser and the server is the webserver hosting the website.
Before you can understand these technologies, you have to understand classic HTTP web traffic first.
HTML5 Server Sent Events (SSE) / EventSource:
The server sends an event to the client when there's new information available.
The server and the client can now send each other messages when new data (on either side) is available.
Comet is a collection of techniques prior to HTML5 which use streaming and long-polling to achieve real time applications. Read more on wikipedia or this article.
You can use PHP with WebSockets, check out Ratchet.