Summary of PHP Abstract Classes

What is an Abstract Class?

• An abstract class in PHP is a class that cannot be instantiated directly.
• It serves as a blueprint for other classes.
• Abstract classes can contain:
  • Abstract methods (without implementation)
  • Non-abstract methods (with implementation)

Key Concepts

• Abstract Method: A method that is declared without an implementation, requiring subclasses to implement it.
• Non-Abstract Method: A method that has a defined implementation, which can be inherited by subclasses.

Creating an Abstract Class

• Use the abstract keyword before the class definition.
• Declare abstract methods using the abstract keyword.

Example:

abstract class Animal {
    // Abstract method
    abstract protected function makeSound();

    // Non-abstract method
    public function eat() {
        echo "Eating...\n";
    }
}

Subclassing an Abstract Class

• A subclass must implement all abstract methods from the parent abstract class.
• The subclass can also inherit non-abstract methods.

Example:

class Dog extends Animal {
    // Implementing the abstract method
    protected function makeSound() {
        echo "Bark!\n";
    }
}

$dog = new Dog();
$dog->makeSound(); // Outputs: Bark!
$dog->eat();       // Outputs: Eating...

Benefits of Using Abstract Classes

• Code Reusability: Shared code in non-abstract methods reduces redundancy.
• Enforcement of Method Implementation: Ensures that certain methods are implemented in subclasses.

Conclusion

Abstract classes provide a way to define a common interface for subclasses while allowing for shared functionality. They are essential for implementing polymorphism in object-oriented programming.

This summary provides a foundational understanding of abstract classes in PHP, making it easier for beginners to grasp the concept and apply it in their coding practices.