Abstract Factory Pattern in C#

Below is a C# implementation of the Abstract Factory design pattern, a Creational pattern, following the Gang of Four (GoF) structure. Each class is placed in its own file and created in an order that avoids dependency issues.

---

Class Creation Order

To avoid dependency issues, create the classes in this order:

1. AbstractProductA & AbstractProductB (Abstract Products)
2. ConcreteProductA1, ConcreteProductA2, ConcreteProductB1, ConcreteProductB2 (Concrete Products)
3. AbstractFactory (Factory Interface)
4. ConcreteFactory1 & ConcreteFactory2 (Factory Implementations)
5. Client Code (Program.cs)

---

1. Abstract Products (IAbstractProductA.cs & IAbstractProductB.cs)

IAbstractProductA.cs

namespace AbstractFactoryPattern
{
    // Abstract Product A
    public interface IAbstractProductA
    {
        void Use();
    }
}

IAbstractProductB.cs

namespace AbstractFactoryPattern
{
    // Abstract Product B
    public interface IAbstractProductB
    {
        void Use();
    }
}

Explanation

IAbstractProductA and IAbstractProductB define the interfaces for two types of products.
Each product type has a Use() method, which will be implemented by concrete products.

---

2. Concrete Products

ConcreteProductA1.cs

using System;

namespace AbstractFactoryPattern
{
    // Concrete Product A1
    public class ConcreteProductA1 : IAbstractProductA
    {
        public void Use()
        {
            Console.WriteLine("Using ConcreteProductA1");
        }
    }
}

ConcreteProductA2.cs

using System;

namespace AbstractFactoryPattern
{
    // Concrete Product A2
    public class ConcreteProductA2 : IAbstractProductA
    {
        public void Use()
        {
            Console.WriteLine("Using ConcreteProductA2");
        }
    }
}

ConcreteProductB1.cs

using System;

namespace AbstractFactoryPattern
{
    // Concrete Product B1
    public class ConcreteProductB1 : IAbstractProductB
    {
        public void Use()
        {
            Console.WriteLine("Using ConcreteProductB1");
        }
    }
}

ConcreteProductB2.cs

using System;

namespace AbstractFactoryPattern
{
    // Concrete Product B2
    public class ConcreteProductB2 : IAbstractProductB
    {
        public void Use()
        {
            Console.WriteLine("Using ConcreteProductB2");
        }
    }
}

Explanation

ConcreteProductA1, ConcreteProductA2 implement IAbstractProductA.
ConcreteProductB1, ConcreteProductB2 implement IAbstractProductB.
These represent different product variations.

---

3. Abstract Factory (IAbstractFactory.cs)

namespace AbstractFactoryPattern
{
    // Abstract Factory Interface
    public interface IAbstractFactory
    {
        IAbstractProductA CreateProductA();
        IAbstractProductB CreateProductB();
    }
}

Explanation:
Defines CreateProductA() and CreateProductB(), which will be implemented by concrete factories.

---

4. Concrete Factories

ConcreteFactory1.cs

namespace AbstractFactoryPattern
{
    // Concrete Factory 1
    public class ConcreteFactory1 : IAbstractFactory
    {
        public IAbstractProductA CreateProductA()
        {
            return new ConcreteProductA1();
        }

        public IAbstractProductB CreateProductB()
        {
            return new ConcreteProductB1();
        }
    }
}

ConcreteFactory2.cs

namespace AbstractFactoryPattern
{
    // Concrete Factory 2
    public class ConcreteFactory2 : IAbstractFactory
    {
        public IAbstractProductA CreateProductA()
        {
            return new ConcreteProductA2();
        }

        public IAbstractProductB CreateProductB()
        {
            return new ConcreteProductB2();
        }
    }
}

Explanation:
ConcreteFactory1 creates ConcreteProductA1 and ConcreteProductB1.
ConcreteFactory2 creates ConcreteProductA2 and ConcreteProductB2.

---

5. Client Code (Program.cs)

using System;

namespace AbstractFactoryPattern
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a factory of type 1
            IAbstractFactory factory1 = new ConcreteFactory1();
            IAbstractProductA productA1 = factory1.CreateProductA();
            IAbstractProductB productB1 = factory1.CreateProductB();

            productA1.Use(); // Output: Using ConcreteProductA1
            productB1.Use(); // Output: Using ConcreteProductB1

            // Create a factory of type 2
            IAbstractFactory factory2 = new ConcreteFactory2();
            IAbstractProductA productA2 = factory2.CreateProductA();
            IAbstractProductB productB2 = factory2.CreateProductB();

            productA2.Use(); // Output: Using ConcreteProductA2
            productB2.Use(); // Output: Using ConcreteProductB2
        }
    }
}

---

Final Explanation

1. Abstract Products (IAbstractProductA, IAbstractProductB): Define interfaces for different types of products.
2. Concrete Products: Implement the abstract product interfaces.
3. Abstract Factory: Declares factory methods for creating products.
4. Concrete Factories: Implement factory methods to produce different products.
5. Client Code: Uses the abstract factory to create product families.

---

Key Takeaways

• ✅ Encapsulation: The client is independent of concrete product classes.
• ✅ Scalability: Easily add new product families without modifying existing code.
• ✅ Consistency: Ensures related products are created together.

Would you like a downloadable version of this file or to have it combined with the C++/PHP HTML examples into a single learning package?

Below is a C++ implementation of the Abstract Factory design pattern, which is a Creational pattern, following the Gang of Four (GoF) structure. Each class is placed in its own file and created in an order that avoids dependency issues.

---

Class Creation Order

To avoid dependency errors, create the classes in this order:

1. AbstractProductA & AbstractProductB (Abstract Products)
2. ConcreteProductA1, ConcreteProductA2, ConcreteProductB1, ConcreteProductB2 (Concrete Products)
3. AbstractFactory (Factory Interface)
4. ConcreteFactory1 & ConcreteFactory2 (Factory Implementations)
5. Client Code (main.cpp)

---

1. AbstractProductA.h & AbstractProductB.h (Abstract Products)

AbstractProductA.h

#ifndef ABSTRACTPRODUCTA_H
#define ABSTRACTPRODUCTA_H

// Abstract Product A
class AbstractProductA {
public:
    virtual void use() = 0; // Pure virtual function
    virtual ~AbstractProductA() {} // Virtual destructor
};

#endif // ABSTRACTPRODUCTA_H

AbstractProductB.h

#ifndef ABSTRACTPRODUCTB_H
#define ABSTRACTPRODUCTB_H

// Abstract Product B
class AbstractProductB {
public:
    virtual void use() = 0;
    virtual ~AbstractProductB() {} // Virtual destructor
};

#endif // ABSTRACTPRODUCTB_H

Explanation

AbstractProductA and AbstractProductB define the interfaces for the two types of products. Each abstract product contains a use() method, which will be implemented by concrete products.

---

2. Concrete Products

ConcreteProductA1.h

#ifndef CONCRETEPRODUCTA1_H
#define CONCRETEPRODUCTA1_H

#include "AbstractProductA.h"
#include <iostream>

// Concrete Product A1
class ConcreteProductA1 : public AbstractProductA {
public:
    void use() override {
        std::cout << "Using ConcreteProductA1" << std::endl;
    }
};

#endif // CONCRETEPRODUCTA1_H

ConcreteProductA2.h

#ifndef CONCRETEPRODUCTA2_H
#define CONCRETEPRODUCTA2_H

#include "AbstractProductA.h"
#include <iostream>

// Concrete Product A2
class ConcreteProductA2 : public AbstractProductA {
public:
    void use() override {
        std::cout << "Using ConcreteProductA2" << std::endl;
    }
};

#endif // CONCRETEPRODUCTA2_H

ConcreteProductB1.h

#ifndef CONCRETEPRODUCTB1_H
#define CONCRETEPRODUCTB1_H

#include "AbstractProductB.h"
#include <iostream>

// Concrete Product B1
class ConcreteProductB1 : public AbstractProductB {
public:
    void use() override {
        std::cout << "Using ConcreteProductB1" << std::endl;
    }
};

#endif // CONCRETEPRODUCTB1_H

ConcreteProductB2.h

#ifndef CONCRETEPRODUCTB2_H
#define CONCRETEPRODUCTB2_H

#include "AbstractProductB.h"
#include <iostream>

// Concrete Product B2
class ConcreteProductB2 : public AbstractProductB {
public:
    void use() override {
        std::cout << "Using ConcreteProductB2" << std::endl;
    }
};

#endif // CONCRETEPRODUCTB2_H

Explanation

ConcreteProductA1, ConcreteProductA2 implement AbstractProductA.
ConcreteProductB1, ConcreteProductB2 implement AbstractProductB.
These represent different product variations.

---

3. AbstractFactory.h (Abstract Factory Interface)

#ifndef ABSTRACTFACTORY_H
#define ABSTRACTFACTORY_H

#include "AbstractProductA.h"
#include "AbstractProductB.h"

// Abstract Factory Interface
class AbstractFactory {
public:
    virtual AbstractProductA* createProductA() = 0;
    virtual AbstractProductB* createProductB() = 0;
    virtual ~AbstractFactory() {} // Virtual destructor
};

#endif // ABSTRACTFACTORY_H

Explanation:
Defines createProductA() and createProductB(), which will be implemented by concrete factories.

---

4. Concrete Factories

ConcreteFactory1.h

#ifndef CONCRETEFACTORY1_H
#define CONCRETEFACTORY1_H

#include "AbstractFactory.h"
#include "ConcreteProductA1.h"
#include "ConcreteProductB1.h"

// Concrete Factory 1
class ConcreteFactory1 : public AbstractFactory {
public:
    AbstractProductA* createProductA() override {
        return new ConcreteProductA1();
    }

    AbstractProductB* createProductB() override {
        return new ConcreteProductB1();
    }
};

#endif // CONCRETEFACTORY1_H

ConcreteFactory2.h

#ifndef CONCRETEFACTORY2_H
#define CONCRETEFACTORY2_H

#include "AbstractFactory.h"
#include "ConcreteProductA2.h"
#include "ConcreteProductB2.h"

// Concrete Factory 2
class ConcreteFactory2 : public AbstractFactory {
public:
    AbstractProductA* createProductA() override {
        return new ConcreteProductA2();
    }

    AbstractProductB* createProductB() override {
        return new ConcreteProductB2();
    }
};

#endif // CONCRETEFACTORY2_H

Explanation:
ConcreteFactory1 creates ConcreteProductA1 and ConcreteProductB1.
ConcreteFactory2 creates ConcreteProductA2 and ConcreteProductB2.

---

5. main.cpp (Client Code)

#include <iostream>
#include "ConcreteFactory1.h"
#include "ConcreteFactory2.h"

int main() {
    // Create a factory of type 1
    AbstractFactory* factory1 = new ConcreteFactory1();
    AbstractProductA* productA1 = factory1->createProductA();
    AbstractProductB* productB1 = factory1->createProductB();

    productA1->use(); // Output: Using ConcreteProductA1
    productB1->use(); // Output: Using ConcreteProductB1

    // Create a factory of type 2
    AbstractFactory* factory2 = new ConcreteFactory2();
    AbstractProductA* productA2 = factory2->createProductA();
    AbstractProductB* productB2 = factory2->createProductB();

    productA2->use(); // Output: Using ConcreteProductA2
    productB2->use(); // Output: Using ConcreteProductB2

    // Cleanup
    delete productA1;
    delete productB1;
    delete factory1;

    delete productA2;
    delete productB2;
    delete factory2;

    return 0;
}

---

Final Explanation

1. Abstract Products (AbstractProductA & AbstractProductB): Define interfaces for different types of products.
2. Concrete Products: Implement the abstract products.
3. Abstract Factory: Declares factory methods for creating products.
4. Concrete Factories: Implement factory methods to produce different products.
5. Client Code: Uses the abstract factory to create product families.

---

Key Takeaways

• ✅ Encapsulation: The client is independent of concrete product classes.
• ✅ Scalability: Easily add new product families without modifying existing code.
• ✅ Consistency: Ensures related products are created together.

Factory Design Pattern in PHP

Here's the detailed breakdown and implementation of the Factory Design Pattern in PHP following the Gang of Four's approach.

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Order of Class Creation

1. Product Interface (Product.php) – Defines the interface that all concrete products must implement.
2. Concrete Products (ConcreteProductA.php and ConcreteProductB.php) – Implement the product interface.
3. Creator (Factory) Interface (Creator.php) – Declares the factory method.
4. Concrete Factories (ConcreteCreatorA.php and ConcreteCreatorB.php) – Implement the factory method to create specific product instances.
5. Client Code (index.php) – Uses the factory to create objects.

---

Factory Design Pattern in PHP

I'll generate the code in individual files, following the correct sequence.

1. Product Interface (Product.php)

<?php
// Product.php
// The Product interface declares the operations that all concrete products must implement.

interface Product {
    public function operation(): string;
}
?>
  

Explanation:
This interface ensures that all products created by the factory implement a common method operation().

---

2. Concrete Products (ConcreteProductA.php and ConcreteProductB.php)

Concrete Product A (ConcreteProductA.php)

<?php
// ConcreteProductA.php
// Implements the Product interface.

require_once "Product.php";

class ConcreteProductA implements Product {
    public function operation(): string {
        return "Result from ConcreteProductA";
    }
}
?>
  

Concrete Product B (ConcreteProductB.php)

<?php
// ConcreteProductB.php
// Implements the Product interface.

require_once "Product.php";

class ConcreteProductB implements Product {
    public function operation(): string {
        return "Result from ConcreteProductB";
    }
}
?>
  

Explanation:
Both ConcreteProductA and ConcreteProductB implement the Product interface.
Each class defines the operation() method, returning a string to identify itself.

---

3. Factory Interface (Creator.php)

<?php
// Creator.php
// The Creator class declares the factory method.

interface Creator {
    public function factoryMethod(): Product;
}
?>
  

Explanation:
This interface defines a method factoryMethod() that must be implemented by all concrete factories to produce a Product.

---

4. Concrete Factories (ConcreteCreatorA.php and ConcreteCreatorB.php)

Concrete Factory A (ConcreteCreatorA.php)

<?php
// ConcreteCreatorA.php
// Implements the Creator interface and produces ConcreteProductA.

require_once "Creator.php";
require_once "ConcreteProductA.php";

class ConcreteCreatorA implements Creator {
    public function factoryMethod(): Product {
        return new ConcreteProductA();
    }
}
?>
  

Concrete Factory B (ConcreteCreatorB.php)

<?php
// ConcreteCreatorB.php
// Implements the Creator interface and produces ConcreteProductB.

require_once "Creator.php";
require_once "ConcreteProductB.php";

class ConcreteCreatorB implements Creator {
    public function factoryMethod(): Product {
        return new ConcreteProductB();
    }
}
?>
  

Explanation:
ConcreteCreatorA and ConcreteCreatorB each implement Creator.
They override factoryMethod() to return an instance of a specific Product (ConcreteProductA or ConcreteProductB).

---

5. Client Code (index.php)

<?php
// index.php
// The client code calls the factory method to create objects.

require_once "ConcreteCreatorA.php";
require_once "ConcreteCreatorB.php";

/**
 * Function to test the factory pattern
 */
function clientCode(Creator $creator) {
    echo "Client: I'm working with " . get_class($creator) . "<br>";
    $product = $creator->factoryMethod();
    echo "Product says: " . $product->operation() . "<br><br>";
}

// Testing both factories
echo "<h2>Factory Method Pattern in PHP</h2>";

echo "<h3>Using ConcreteCreatorA:</h3>";
clientCode(new ConcreteCreatorA());

echo "<h3>Using ConcreteCreatorB:</h3>";
clientCode(new ConcreteCreatorB());

?>
  

Explanation:
The clientCode() function expects an object that implements Creator.
It calls the factoryMethod() to create a product and prints the result.
The index.php script tests both ConcreteCreatorA and ConcreteCreatorB, demonstrating the Factory Pattern in action.

---

Final Thoughts

This structured approach ensures:

• Clear separation of concerns (each class has a single responsibility).
• Encapsulation of object creation in the factory classes.
• Scalability (new products can be introduced without altering existing code).

Java Creational Factory

📁 File Structure

/FactoryMethodPattern
│── Product.java
│── ConcreteProductA.java
│── ConcreteProductB.java
│── Creator.java
│── ConcreteCreatorA.java
│── ConcreteCreatorB.java
│── Main.java
    

1. Product.java (Abstract Product Interface)

// Abstract Product interface
public interface Product {
    void use();
}
    

2. ConcreteProductA.java & ConcreteProductB.java (Concrete Products)

ConcreteProductA.java

// Concrete Product A
public class ConcreteProductA implements Product {
    @Override
    public void use() {
        System.out.println("Using ConcreteProductA");
    }
}
    

ConcreteProductB.java

// Concrete Product B
public class ConcreteProductB implements Product {
    @Override
    public void use() {
        System.out.println("Using ConcreteProductB");
    }
}
    

3. Creator.java (Abstract Factory Class)

// Abstract Creator class
public abstract class Creator {
    // Factory Method: Must be implemented by concrete creators
    public abstract Product factoryMethod();
}
    

4. ConcreteCreatorA.java & ConcreteCreatorB.java (Factory Implementations)

ConcreteCreatorA.java

// Concrete Creator A
public class ConcreteCreatorA extends Creator {
    @Override
    public Product factoryMethod() {
        return new ConcreteProductA();
    }
}
    

ConcreteCreatorB.java

// Concrete Creator B
public class ConcreteCreatorB extends Creator {
    @Override
    public Product factoryMethod() {
        return new ConcreteProductB();
    }
}
    

5. Main.java (Client Code)

public class Main {
    public static void main(String[] args) {
        // Create a factory for ProductA
        Creator creatorA = new ConcreteCreatorA();
        Product productA = creatorA.factoryMethod();
        productA.use(); // Output: Using ConcreteProductA

        // Create a factory for ProductB
        Creator creatorB = new ConcreteCreatorB();
        Product productB = creatorB.factoryMethod();
        productB.use(); // Output: Using ConcreteProductB
    }
}
    

🎯 Key Takeaways

• ✅ Encapsulation: The client does not know which concrete product it gets.
• ✅ Scalability: Easily add new products and factories.
• ✅ Decoupling: The factory method isolates the creation logic.

C# Creational Factory

📁 File Structure

/FactoryMethodPattern
│── IProduct.cs
│── ConcreteProductA.cs
│── ConcreteProductB.cs
│── Creator.cs
│── ConcreteCreatorA.cs
│── ConcreteCreatorB.cs
│── Program.cs
    

1. IProduct.cs (Abstract Product Interface)

namespace FactoryMethodPattern
{
    // Abstract Product Interface
    public interface IProduct
    {
        void Use();
    }
}
    

2. ConcreteProductA.cs & ConcreteProductB.cs (Concrete Products)

ConcreteProductA.cs

using System;

namespace FactoryMethodPattern
{
    // Concrete Product A
    public class ConcreteProductA : IProduct
    {
        public void Use()
        {
            Console.WriteLine("Using ConcreteProductA");
        }
    }
}
    

ConcreteProductB.cs

using System;

namespace FactoryMethodPattern
{
    // Concrete Product B
    public class ConcreteProductB : IProduct
    {
        public void Use()
        {
            Console.WriteLine("Using ConcreteProductB");
        }
    }
}
    

3. Creator.cs (Abstract Factory Class)

namespace FactoryMethodPattern
{
    // Abstract Creator
    public abstract class Creator
    {
        // Factory Method: Must be implemented by concrete creators
        public abstract IProduct FactoryMethod();
    }
}
    

4. ConcreteCreatorA.cs & ConcreteCreatorB.cs (Factory Implementations)

ConcreteCreatorA.cs

namespace FactoryMethodPattern
{
    // Concrete Creator A
    public class ConcreteCreatorA : Creator
    {
        public override IProduct FactoryMethod()
        {
            return new ConcreteProductA();
        }
    }
}
    

ConcreteCreatorB.cs

namespace FactoryMethodPattern
{
    // Concrete Creator B
    public class ConcreteCreatorB : Creator
    {
        public override IProduct FactoryMethod()
        {
            return new ConcreteProductB();
        }
    }
}
    

5. Program.cs (Client Code)

using System;

namespace FactoryMethodPattern
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a factory for ProductA
            Creator creatorA = new ConcreteCreatorA();
            IProduct productA = creatorA.FactoryMethod();
            productA.Use(); // Output: Using ConcreteProductA

            // Create a factory for ProductB
            Creator creatorB = new ConcreteCreatorB();
            IProduct productB = creatorB.FactoryMethod();
            productB.Use(); // Output: Using ConcreteProductB
        }
    }
}
    

🎯 Key Takeaways

• ✅ Encapsulation: The client does not know which concrete product it gets.
• ✅ Scalability: Easily add new products and factories.
• ✅ Decoupling: The factory method isolates the creation logic.

C++ Creational Factory

📁 File Structure

/ProjectFolder
│── Product.h
│── ConcreteProduct.h
│── ConcreteProduct.cpp
│── Creator.h
│── ConcreteCreator.h
│── ConcreteCreator.cpp
│── main.cpp
    

1. Product.h (Abstract Product)

#ifndef PRODUCT_H
#define PRODUCT_H

#include <iostream>

// Abstract Product class
class Product {
public:
    virtual void use() = 0; // Pure virtual function to be implemented by concrete products
    virtual ~Product() {} // Virtual destructor for proper cleanup
};

#endif // PRODUCT_H
    

2. ConcreteProduct.h & ConcreteProduct.cpp (Concrete Implementations)

ConcreteProduct.h

#ifndef CONCRETEPRODUCT_H
#define CONCRETEPRODUCT_H

#include "Product.h"

// Concrete Product class
class ConcreteProductA : public Product {
public:
    void use() override; // Implementation of abstract method
};

class ConcreteProductB : public Product {
public:
    void use() override;
};

#endif // CONCRETEPRODUCT_H
    

ConcreteProduct.cpp

#include "ConcreteProduct.h"

// Implement ConcreteProductA's behavior
void ConcreteProductA::use() {
    std::cout << "Using ConcreteProductA" << std::endl;
}

// Implement ConcreteProductB's behavior
void ConcreteProductB::use() {
    std::cout << "Using ConcreteProductB" << std::endl;
}
    

3. Creator.h (Abstract Factory Class)

#ifndef CREATOR_H
#define CREATOR_H

#include "Product.h"

// Abstract Factory class
class Creator {
public:
    virtual Product* factoryMethod() = 0; // Factory method to create objects
    virtual ~Creator() {} // Virtual destructor
};

#endif // CREATOR_H
    

4. ConcreteCreator.h & ConcreteCreator.cpp (Factory Implementations)

ConcreteCreator.h

#ifndef CONCRETECREATOR_H
#define CONCRETECREATOR_H

#include "Creator.h"
#include "ConcreteProduct.h"

// Concrete Creator for ProductA
class ConcreteCreatorA : public Creator {
public:
    Product* factoryMethod() override;
};

// Concrete Creator for ProductB
class ConcreteCreatorB : public Creator {
public:
    Product* factoryMethod() override;
};

#endif // CONCRETECREATOR_H
    

ConcreteCreator.cpp

#include "ConcreteCreator.h"

// Factory method returns an instance of ConcreteProductA
Product* ConcreteCreatorA::factoryMethod() {
    return new ConcreteProductA();
}

// Factory method returns an instance of ConcreteProductB
Product* ConcreteCreatorB::factoryMethod() {
    return new ConcreteProductB();
}
    

5. main.cpp (Client Code)

#include <iostream>
#include "ConcreteCreator.h"

int main() {
    // Create a factory for ProductA
    Creator* creatorA = new ConcreteCreatorA();
    Product* productA = creatorA->factoryMethod();
    productA->use(); // Output: Using ConcreteProductA

    // Create a factory for ProductB
    Creator* creatorB = new ConcreteCreatorB();
    Product* productB = creatorB->factoryMethod();
    productB->use(); // Output: Using ConcreteProductB

    // Cleanup
    delete productA;
    delete creatorA;
    delete productB;
    delete creatorB;

    return 0;
}
    

🎯 Key Takeaways

• Encapsulation: The factory method ensures the client only depends on the abstract Product interface, not concrete classes.
• Scalability: Adding new products only requires adding new concrete products and their corresponding creators.
• Decoupling: The client does not depend on the actual product classes.

PHP Creational Singelton

📁 File Structure

1. Singleton.php - This file contains the actual Singleton class.
2. index.php - This demonstrates the Singleton pattern in action.
3. SomeClass.php - An additional class to showcase how the Singleton can be used with other classes.
    

1. Singleton.php

<?php

class Singleton {
    private static $instance = null;

    // The constructor is private so that the object can't be instantiated from outside
    private function __construct() { }

    // Cloning is disabled to ensure the uniqueness of the instance
    private function __clone() { }

    // This method returns the singleton instance of this class
    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new Singleton();
        }
        return self::$instance;
    }
}

?>
    

2. SomeClass.php

<?php

class SomeClass {
    private $singleton;

    public function __construct() {
        $this->singleton = Singleton::getInstance();
    }

    public function doSomething() {
        echo "Using the Singleton instance within SomeClass!";
    }
}

?>
    

3. index.php

<?php

include 'Singleton.php';
include 'SomeClass.php';

// Trying to get two instances of Singleton
$instance1 = Singleton::getInstance();
$instance2 = Singleton::getInstance();

// Both instances are the same
if ($instance1 === $instance2) {
    echo "Both instances are the same!<br>";
}

// Demonstrating the use of Singleton in another class
$obj = new SomeClass();
$obj->doSomething();

?>
    

🛠 Explanation

• Singleton Class:
  • Private static variable $instance: This holds the only instance of the class.
  • Private Constructor: To prevent any external instantiations.
  • Private __clone Method: To prevent the object from being cloned.
  • getInstance Method: Ensures only one instance is created.
• SomeClass:
  • Demonstrates how we might use the Singleton within another class.
• index.php:
  • Demonstrates that both instances retrieved from Singleton::getInstance() are the same.
  • Shows the usage of the Singleton instance within another class.

⚠️ Important Note

When working with the Singleton pattern, ensure you genuinely need a singleton. Overusing this pattern can lead to design issues and difficulties in testing.