Abstraction in PHP (Abstract Classes & Methods)

Introduction

What is Abstraction?

Abstraction means hiding implementation details and showing only what is necessary.

In simple words:

You define what a class must do, not how it will do it.

Abstraction focuses on design, not implementation.

How Abstraction is Achieved in PHP?

In PHP, abstraction is implemented using:

• Abstract classes
• Abstract methods

What is an Abstract Class?

An abstract class:

• Cannot be instantiated (you cannot create its object)
• Can contain abstract and non-abstract methods
• Can contain properties
• Is meant to be extended by child classes

In PHP, we use the abstract keyword to declare an abstract class.

Abstract Class Syntax

abstract class ClassName {
    abstract public function methodName();
}

Example: Abstract Class in PHP

<?php
abstract class Payment {
    abstract public function pay($amount);

    public function paymentInfo() {
        echo "Processing payment...";
    }
}
?>

In this example:

• Payment is an abstract class.
• pay() is an abstract method (no body).
• paymentInfo() is a normal method.

What is an Abstract Method?

An abstract method:

• Is declared using the abstract keyword
• Does not contain a body
• Must be implemented in the child class

Syntax:

abstract public function methodName();

Notice that there is no {} body.

Abstract Method Rules

• Must be declared using abstract keyword
• Must not have a body
• Child class must implement it

Implementing Abstract Class

Now let’s create child classes:

<?php
class CardPayment extends Payment {
    public function pay($amount) {
        echo "Paid ₹$amount using Card";
    }
}

$payment1 = new CardPayment();
$payment1->pay(500);
$payment1->paymentInfo();
$payment2 = new UpiPayment();
$payment2->pay(1000);
?>

Explanation

• Both CardPayment and UpiPayment extend Payment.
• Both are forced to implement pay() method.
• They follow the same structure but provide different logic.

This ensures design consistency across the application.

Important Rules of Abstract Classes

1. You cannot create object of an abstract class.
   ❌ $obj = new Payment();
2. If a class contains at least one abstract method, it must be declared abstract.
3. Child classes must implement all abstract methods.
4. Abstract methods cannot have a body.

Multiple Child Classes

<?php
class UpiPayment extends Payment {
    public function pay($amount) {
        echo "Paid ₹$amount using UPI";
    }
}
?>

Both classes follow the same structure but implement different payment logic.

Why Abstraction is Important?

Abstraction helps developers create a clear structure for large applications by separating required functionality from actual implementation.

It allows you to define common rules that all child classes must follow while still giving flexibility in how those rules are implemented.

Abstraction helps you:

• Enforce consistency across multiple classes
• Create scalable and maintainable architecture
• Reduce code duplication
• Separate design from implementation
• Share common functionality while requiring specific behavior

This makes applications cleaner, easier to manage, and more professional.

Abstraction vs Encapsulation

Real-World Example

Imagine you are building a payment system.

You create an abstract class Payment.

It may contain:

• abstract method processPayment()
• normal method paymentReceipt()

Every payment method like:

• CreditCard
• PayPal
• UPI

Must implement processPayment().

This ensures that every payment method follows a standard structure.

Abstract Class vs Normal Class

Common Mistakes

❌ Creating object of abstract class
❌ Not implementing abstract methods
❌ Mixing abstraction with concrete logic
❌ Forgetting abstract keyword

Practical Tasks

• Create an abstract class called Shape.
• Add:
  • abstract method calculateArea()
  • normal method displayShape()
• Then create two child classes:
  • Circle
  • Rectangle
• Implement calculateArea() in both classes.
• Create objects and test them.

Summary

• Abstract class cannot be instantiated
• It may contain abstract and normal methods
• Abstract methods must be implemented by child classes
• It helps in creating structured and scalable applications

Abstract classes provide a blueprint for other classes and enforce consistent behavior.

In the next tutorial, we’ll learn about Interfaces in PHP.