PHP Abstract Class

In PHP, an abstract class is a class that cannot be instantiated and may contain abstract methods. Abstract classes are often used to define a blueprint for other classes, providing common functionality while allowing derived classes to implement specific details.

Syntax

abstract class AbstractClass {
  // Abstract method declaration
  abstract protected function abstractMethod();
  
  // Regular method with implementation
  public function concreteMethod() {
    // Method implementation
  }
}

Example

Here's an example of an abstract class in PHP:

abstract class Shape {
  abstract protected function calculateArea();
}

class Circle extends Shape {
  private $radius;

  public function __construct($radius) {
    $this->radius = $radius;
  }

  protected function calculateArea() {
    return pi() * $this->radius * $this->radius;
  }
}

Explanation

In the example, Shape is an abstract class with an abstract method calculateArea(). The Circle class extends Shape and provides an implementation for the calculateArea() method.

• Abstract classes are declared using the abstract keyword.
• Abstract methods are declared using the abstract keyword and must be implemented by derived classes.

Use

Abstract classes in PHP are used for:

• Defining a common interface for multiple related classes.
• Enforcing a structure that derived classes must follow.
• Providing a level of abstraction for shared functionality.

Important Points

• Abstract classes cannot be instantiated directly; they are meant to be subclassed.
• Abstract methods must be implemented by any concrete (non-abstract) subclass.
• Abstract classes can have both abstract and regular (concrete) methods.

Summary

In summary, PHP abstract classes provide a way to define common functionality that should be shared among multiple classes while allowing each class to implement specific details. They contribute to code organization, reusability, and the creation of a structured class hierarchy.