php 52 lines · 9 steps

Server-Sent Events in Laravel

A controller streams live notifications to the browser over a long-lived HTTP connection using Server-Sent Events.

Explained by highlit

Laravel Advanced server-sent-events streaming long-polling real-time http-headers

1<?php
2 
3namespace App\Http\Controllers;
4 
5use Illuminate\Http\Request;
6use Symfony\Component\HttpFoundation\StreamedResponse;
7 
8class EventStreamController extends Controller
9{
10    public function stream(Request $request): StreamedResponse
11    {
12        $response = new StreamedResponse(function () use ($request) {
13            $lastId = (int) $request->header('Last-Event-ID', 0);
14 
15            while (! connection_aborted()) {
16                $events = Notification::query()
17                    ->where('id', '>', $lastId)
18                    ->orderBy('id')
19                    ->limit(20)
20                    ->get();
21 
22                foreach ($events as $event) {
23                    $lastId = $event->id;
24 
25                    echo 'id: ' . $event->id . "\n";
26                    echo 'event: ' . $event->type . "\n";
27                    echo 'data: ' . json_encode([
28                        'title' => $event->title,
29                        'body' => $event->body,
30                        'at' => $event->created_at->toIso8601String(),
31                    ]) . "\n\n";
32                }
33 
34                echo ": heartbeat\n\n";
35 
36                if (ob_get_level() > 0) {
37                    ob_flush();
38                }
39                flush();
40 
41                sleep(3);
42            }
43        });
44 
45        $response->headers->set('Content-Type', 'text/event-stream');
46        $response->headers->set('Cache-Control', 'no-cache');
47        $response->headers->set('Connection', 'keep-alive');
48        $response->headers->set('X-Accel-Buffering', 'no');
49 
50        return $response;
51    }
52}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Server-Sent Events keep one HTTP connection open and push newline-delimited text frames instead of polling repeatedly.
2Tracking a last-seen id lets the stream resume exactly where the client left off after a reconnect.
3Explicit output flushing and buffering-disabled headers are essential to actually deliver events as they happen.

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