Notification Service

Quick Introduction

Notification Service is a single PHP idea you'll use in almost every backend project.

In this lesson you learn only notification service — not five topics at once. By the end you can write a small working example and explain it in an interview.

We connect each lesson to our course projects: Login System, Blog CMS, REST API, Inventory, Employee Management, and E-Commerce Backend.

Business Problem

You're building the E-Commerce Backend. After a user signs in, you need notification service working correctly before storing data or showing a dashboard.

Without understanding Notification Service, the team ships bugs: wrong totals, broken sessions, or type errors that only appear in production. This lesson fixes that with one clear pattern you can copy into your project today.

Core Concept

• Notification Service is one focused idea — learn it before mixing with other PHP topics.
• Use it in PHP 8.3+ with declare(strict_types=1); at the top of every file.
• Our course project (E-Commerce Backend) uses notification service in real handlers.
• Run small scripts with php file.php after each change — don't just read.
• Interviewers ask for a one-minute explanation plus a tiny code sample.

Syntax

Core syntax for Notification Service. Every keyword below appears in production PHP — Laravel and Symfony use the same primitives under the hood.

declare(strict_types=1);

Keywords: declare · strict_types · namespace

Step-by-Step Example

Run this script locally. Change one value, run again, and watch what changes.

<?php
declare(strict_types=1);

namespace Notify;

enum Channel: string { case Email = 'email'; case Sms = 'sms'; case Push = 'push'; }

final readonly class Notification {
    public function __construct(
        public int $userId,
        public string $template,
        public array $data,
        public Channel $channel,
    ) {}
}

final class NotificationDispatcher {
    /** @param array<string, callable> $handlers channel => handler */
    public function __construct(private array $handlers) {}

    public function send(Notification $n): void {
        ($this->handlers[$n->channel->value] ?? throw new InvalidArgumentException('Unknown channel'))($n);
    }
}

Line by line

1. — part of the notification service example; run the file to see the result.
2. declare(strict_types=1); — turns on strict type checking for this file.
3. namespace Notify; — part of the notification service example; run the file to see the result.
4. enum Channel: string { case Email = 'email'; case Sms = 'sms'; case Push = 'push'; } — part of the notification service example; run the file to see the result.
5. final readonly class Notification { — part of the notification service example; run the file to see the result.

User #42 (user@example.com) balance $19.99

Real-World Example

In the E-Commerce Backend, notification service appears in a single request handler — not spread across ten files. Keep the example small, test it with php, then paste the pattern into your project branch.

<?php
declare(strict_types=1);

// TODO: Notification Service exercise for E-Commerce Backend