Understanding SSE (Server-Sent Events) in PHP with a Practical Demo Project

Server-Sent Events (SSE) is a powerful and efficient way to establish a one-way communication channel from the server to the client. Unlike WebSockets, which allow two-way communication, SSE is specifically designed for pushing real-time updates from the server to the browser. In this blog, we will delve into the concept of SSE in PHP, understand how it works, and take a look at a demo project to clarify its application.

We will explore how SSE is ideal for applications like live scores, chat applications, and any scenario where real-time updates are required without constant client requests. With PHP being one of the most widely used server-side languages, implementing SSE in PHP allows developers to create efficient real-time communication systems with minimal overhead.

By the end of this post, you’ll have a clear understanding of how to implement SSE in PHP and how it compares with other real-time web technologies like WebSockets.

What is Server-Sent Events (SSE) ?

Server-Sent Events (SSE) is a web standard used for pushing updates from the server to the browser in real-time. It enables a one-way connection where the server can continuously send data to the client after an initial HTTP request. Unlike traditional client-server communication, where the client has to repeatedly make requests (polling) to get updates, SSE creates a persistent connection.

The key features of SSE are:

• One-Way Communication: The server pushes data to the client, while the client listens for updates.
• Automatic Reconnection: If the connection drops, SSE automatically attempts to reconnect.
• Text-Based Protocol: SSE works with plain text or UTF-8 encoded data streams.

SSE is highly efficient for tasks like:

• Live news feeds
• Stock price updates
• Real-time notifications
• Progress updates in long-running tasks

In comparison to WebSockets, which supports two-way communication, SSE is lighter, easier to implement, and ideal for scenarios where the server needs to push updates periodically or based on events.

How SSE Works in PHP :

The beauty of SSE lies in its simplicity. Implementing it in PHP involves creating a PHP script that continuously sends data to the client. The key steps to implementing SSE are:

1. Create the SSE Endpoint: A PHP file serves as the endpoint for sending real-time updates. This script uses a special content type (text/event-stream) and outputs the data in the SSE format.
2. Client-Side Listener: On the client side, we create an EventSource object in JavaScript to connect to the server and receive updates.

Here’s a breakdown of how SSE works with PHP:

• Step 1: The client makes a request to the server by initializing an EventSource object in JavaScript. This object opens a persistent connection to the PHP file that serves as the SSE endpoint.
• Step 2: The PHP script sends updates in a specific format that is recognized by the client. The format consists of an event type, message ID, and the actual data. PHP uses the echo function to send this data periodically.
• Step 3: The browser listens for incoming data and processes it as soon as the server sends it. The connection remains open until it’s explicitly closed by the client or server.

To Download Demo Project click here