Final classes and methods in PHP - Mini Project: Build & Apply

Final classes and methods in PHP

📖 Scenario: You are building a simple PHP program to manage vehicles. Some vehicles should not be changed further to keep their behavior safe and consistent.

🎯 Goal: Learn how to use final keyword in PHP to prevent classes and methods from being extended or overridden.

📋 What You'll Learn

Create a class with the final keyword

Create a method with the final keyword

Try to extend a final class (commented out to avoid error)

Try to override a final method (commented out to avoid error)

Print output from the final class method

💡 Why This Matters

🌍 Real World

Final classes and methods are used to protect critical parts of code from accidental changes, ensuring stability and security.

💼 Career

Understanding final classes and methods is important for writing robust PHP applications and working with frameworks that use them.

1

Create a final class

Create a final class called Vehicle with a public method startEngine that returns the string 'Engine started'.

PHP

# Your code here

Need a hint?

Use final class Vehicle to prevent extension.

2

Add a final method

Inside the Vehicle class, add a final public method called stopEngine that returns the string 'Engine stopped'.

PHP

<?php
final class Vehicle {
    public function startEngine() {
        return 'Engine started';
    }
    // Add final method stopEngine here
}

Need a hint?

Use final public function stopEngine() to prevent overriding.

3

Attempt to extend the final class (commented out)

Add a new class called Car that tries to extend Vehicle. Comment out this code to avoid errors.

PHP

<?php
final class Vehicle {
    public function startEngine() {
        return 'Engine started';
    }
    final public function stopEngine() {
        return 'Engine stopped';
    }
}
// Try to extend Vehicle class here (commented out)

Need a hint?

Extending a final class causes error, so comment it out.

4

Print output from Vehicle methods

Create an object $vehicle of class Vehicle and print the results of calling startEngine() and stopEngine() methods.

PHP

<?php
final class Vehicle {
    public function startEngine() {
        return 'Engine started';
    }
    final public function stopEngine() {
        return 'Engine stopped';
    }
}
// class Car extends Vehicle {
// }

// Create Vehicle object and print method outputs
# Your code here

Need a hint?

Create object with new Vehicle() and use print() to show results.