An article explaining in detail how to quickly create a simple event flow in Laravel

This article brings you relevant knowledge about Laravel event flow. It mainly introduces what event flow is and how to create a simple event flow in Laravel. Interested friends should take a look. I hope everyone has to help.

Introduction

Event streaming provides you with a way to send events to the client without reloading the page. This is useful for updating the user interface when live changes are made to the database.

Unlike traditional long polling using AJAX requests, in which multiple requests are sent to the server and a new connection is established each time, the event stream is sent to the client in real time in a single request .

In this article, I will show you how to create a simple event stream in Laravel.

Prerequisites

Before you begin, you need to have Laravel installed on your machine.

I will be using the DigitalOcean Ubuntu Droplet in this demo. If you'd like, you can use my affiliate code to get free $100 DigitalOcean credits to launch your own server!

If you haven't already, you can follow the steps in this tutorial:

• How to Install Laravel on DigitalOcean with 1-Click

Or you can install it using this awesome script:

• LaraSail

Create a Controller

Let's start by creating a controller that handles the event stream.

Use the following command:

php artisan make:controller EventStreamController

This will create a new controller in the App\Http\Controllers directory.

Adding Event Streaming Methods

Once we have created our controller, we need to add the stream method to it. This method will be used to send a stream of events.

Open the EventStreamController.php file and add the following code:

<?php namespace App\Http\Controllers;use Carbon\Carbon;use App\Models\Trade;class StreamsController extends Controller{
    /**
     * 事件流代码
     *
     * @return \Illuminate\Http\Response
     */
    public function stream(){
        return response()->stream(function () {
            while (true) {
                echo "event: ping\n";
                $curDate = date(DATE_ISO8601);
                echo 'data: {"time": "' . $curDate . '"}';
                echo "\n\n";

                $trades = Trade::latest()->get();
                echo 'data: {"total_trades":' . $trades->count() . '}' . "\n\n";

                $latestTrades = Trade::with('user', 'stock')->latest()->first();
                if ($latestTrades) {
                    echo 'data: {"latest_trade_user":"' . $latestTrades->user->name . '", "latest_trade_stock":"' . $latestTrades->stock->symbol . '", "latest_trade_volume":"' . $latestTrades->volume . '", "latest_trade_price":"' . $latestTrades->stock->price . '", "latest_trade_type":"' . $latestTrades->type . '"}' . "\n\n";
                }

                ob_flush();
                flush();

                // 如果客户端中止连接，则中断循环（关闭页面）
                if (connection_aborted()) {break;}
                usleep(50000); // 50ms
            }
        }, 200, [
            'Cache-Control' => 'no-cache',
            'Content-Type' => 'text/event-stream',
        ]);
    }}

The main things to note here are:

• We use response()->stream() method to create an event stream.
• Then we have an infinite loop that sends a stream of events every 50ms.
• If the client aborts the connection, we use ob_flush() and flush() to send the event stream.
• We use sleep() to wait 50ms before sending the next event.
• We use connection_aborted() to break the loop if the client aborts the connection.
• We use the Carbon\Carbon class to get the current date.
• We use the App\Models\Trade model to get the latest transactions. This is for demonstration only, you can use any model you want.
• Set the Content-Type header to text/event-stream to tell the browser that the response is an event stream.

Enable output buffering

In order for the above code to work properly, we need to enable output buffering in your PHP.ini file. This is done by adding the following line to the php.ini file:

output_buffering = On

It may be necessary to reload the PHP-FPM service after making this change. Or if you are using Apache, you can restart Apache.

Add route

When requesting the /stream route, we want to call the ``stream` method.

The route will be added to the routes/web.php file as follows:

use App\Http\Controllers\StreamsController;Route::get('/stream', [StreamsController::class, 'stream']);

Using the event flow from the frontend

You can use Front-end frameworks such as Vue.js are used to handle event streams. But for this demo, I'm going to use pure Javascript.

The JavaScript snippet added to the blade template looks like this:

const eventSource = new EventSource('/stream');eventSource.onmessage = function(event) {
    const data = JSON.parse(event.data);
    if (data.time) {
        document.getElementById('time').innerHTML = data.time;
    }
    const newElement = document.createElement("li");
    const eventList = document.getElementById("list");

    newElement.textContent = "message: " + event.data;
    eventList.appendChild(newElement);}

To see this in action, you can try the following demo! [Related recommendations: laravel video tutorial]

Demo project

If you want to understand how event streaming works, you can check out the demo project I created:

Laravel EventStream: Live Stock Trading Dashboard using Laravel and Materialize

Demo project not only shows the event stream but also has a simple front-end dashboard and uses Materialize As a streaming database.

SSE vs WebSockets

Event streaming is great and easy to use, but it also has some advantages and disadvantages compared to other streaming protocols like WebSockets.

For example, SSE is one-way, which means that once the connection is established, the server can only send data to the client, and the client cannot send data back to the server.

Unlike long polling, with WebSockets you have only one connection to the server, similar to SSE (Server Sent Events). The connection is duplex, which means you can send and receive data from the server.

If you want to learn more about the differences between SSE and WebSockets, check out this great video by Martin Chaov: Links

Conclusion

Related For more information on event streaming, check out this documentation from Mozilla here:

• Event Streaming in the Web Platform

There, You'll find a more in-depth explanation of event streaming and how it works.

For more information about Materialize, watch this video here: Link

Hope you enjoyed this tutorial!

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