Observer Pattern Simulation in Pure PHP

This project is a simple Event-Driven system built with pure PHP using OOP principles. It demonstrates the Observer Design Pattern in a real-world scenario where a file download triggers multiple independent observers such as logging, analytics, and counters.

Note that no actual file is downloaded, This is just a test

🌐 Visit Demo

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How it works

1️⃣ User clicks download button in index.php

2️⃣ FileDownload use case is triggered

3️⃣ A DownloadEvent is created containing:

• file id
• file slug
• file name
• user IP
• timestamp

4️⃣ Event is passed to Subject (FileDownload)

5️⃣ All registered observers are notified:

• Analytics → tracks event
• Counter → increases download count
• Logger → saves log

6️⃣ Each observer reacts independently without affecting others

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Design Pattern Used

Observer Pattern

• Subject: UseCases/FileDownload.php
• Event: Events/DownloadEvent.php
• Observers:
  • Observers/Logger.php
  • Observers/Counter.php
  • Observers/Analytics.php

🟡 The Subject does not know anything about observers.
🟡 It only broadcasts an event, and observers react independently.

Implemented by Hesam kazembeygi

📌 My Website

📌 My LinkedIn

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License

PHP Observer is open-sourced software licensed under the MIT license.