What is the working principle of PHP SSE technology?

Server-Sent Events (SSE) is a technology used for achieving one-way real-time communication between a client and server. It works by sending event streams from the server to the client in order to push data from the server to the client.

The working principle of SSE is as follows:

1. Clients connect with the server by creating an EventSource object.
2. The server sets the response header Content-Type as text/event-stream and sends a data message once the connection is established, which marks the beginning of the data stream.
3. The server must adhere to a specific format when sending data, which means each data message must start with “data:” and end with two line breaks “\n\n”.
4. The client handles the data received from the server by listening to the message event.
5. The client can update the page content or perform other operations based on the received data.

Compared to other real-time communication technologies like WebSockets, SSE technology is simpler and easier to use, suitable for scenarios that do not require two-way communication, such as displaying real-time data and notifications.