In the world of software design, patterns play a crucial role in solving common problems efficiently. One such powerful behavioral design pattern is the Strategy Pattern. In this blog, we will explore the concept of the Strategy Pattern, understand its use cases, and learn how to implement it effectively in PHP.

What is the Strategy Pattern?

The Strategy Pattern is a behavioral design pattern that defines a family of algorithms, encapsulates each one, and makes them interchangeable. This pattern allows a class’s behavior to be selected at runtime, promoting flexibility and code reusability.

In simpler terms, the Strategy Pattern allows you to switch between different algorithms or strategies without modifying the class that uses them.

Why Use the Strategy Pattern?

• Eliminates Conditional Logic: Avoids large if-else or switch blocks.
• Open/Closed Principle: You can add new strategies without altering existing code.
• Improved Maintainability: Each strategy resides in its own class, making it easier to debug and maintain.
• Runtime Flexibility: Switch between strategies dynamically based on the requirements.

Real-World Use Cases

• Payment Gateways: Switch between PayPal, Stripe, or Authorize.Net for payment processing.
• Sorting Algorithms: Use different sorting algorithms based on dataset size.
• Authentication Mechanisms: Support multiple authentication strategies like OAuth, JWT, or Session-based authentication.

Strategy Pattern in PHP: Example Implementation

Let’s implement the Strategy Pattern using a real-world example: Payment Gateways.

Step 1: Define the Strategy Interface

<?php
interface PaymentGateway {
    public function processPayment(float $amount);
}

Step 2: Create Concrete Strategies

PayPal Gateway

<?php
class PayPalGateway implements PaymentGateway {
    public function processPayment(float $amount) {
        echo "Processing $$amount payment through PayPal.\n";
    }
}

Stripe Gateway

<?php
class StripeGateway implements PaymentGateway {
    public function processPayment(float $amount) {
        echo "Processing $$amount payment through Stripe.\n";
    }
}

Step 3: Create Context Class

<?php
class PaymentProcessor {
    private PaymentGateway $gateway;
    public function __construct(PaymentGateway $gateway) {
        $this->gateway = $gateway;
    }
    public function setGateway(PaymentGateway $gateway) {
        $this->gateway = $gateway;
    }
    public function pay(float $amount) {
        $this->gateway->processPayment($amount);
    }
}

Step 4: Client Code

<?php
$processor = new PaymentProcessor(new PayPalGateway());
$processor->pay(100.50);

$processor->setGateway(new StripeGateway());
$processor->pay(200.75);

Output:

Processing $100.5 payment through PayPal.
Processing $200.75 payment through Stripe.

Advantages of the Strategy Pattern

• Clear separation of algorithms.
• Easy to add new strategies without modifying the existing code.
• Enhances code reusability.
• Promotes clean architecture and SOLID principles.

When to Use the Strategy Pattern?

• When you have multiple ways of performing a specific task.
• When you want to isolate and encapsulate algorithm variations.
• When conditional statements become too complex and unmanageable.

Final Thoughts

The Strategy Pattern is an excellent choice when your application requires flexibility in choosing an algorithm or behavior at runtime. It helps you write cleaner, more modular, and maintainable code.

If you’re building a system with varying behaviors (like payment gateways, sorting mechanisms, or authentication), the Strategy Pattern is your go-to solution.