Implementing a Real-World Feature Across Drupal, Symfony, and Laravel

Feature: E-Commerce “Discount Code Validator”

Requirement:

• When a user applies a discount code during checkout:
  • Validate the code
  • Check expiration and usage limits
  • Calculate discount
  • Return an updated order total
• Must be extensible for future promotion types

This feature is small but touches services, events, plugins, and DI—perfect for comparing modular approaches.

Dependency Injection Without Pain: Symfony, Laravel, and Drupal Explained

Introduction

Dependency Injection (DI) is a cornerstone of modern PHP frameworks, but many developers—especially those coming from Drupal—find it confusing. Why inject services instead of calling them directly? How do DI containers differ between Drupal, Symfony, and Laravel?

In this article, we’ll break it down with practical examples, showing how to use DI without headaches across these three systems.

1. What is Dependency Injection?

Simply put: