Constants in classes in PHP - Mini Project: Build & Apply

Constants in classes

📖 Scenario: Imagine you are creating a simple program to represent different types of vehicles. Each vehicle type has a fixed number of wheels that never changes. You want to store these fixed numbers as constants inside a class to keep your code organized and clear.

🎯 Goal: You will create a PHP class called Vehicle with constants for different vehicle types and their fixed number of wheels. Then, you will print out the number of wheels for a specific vehicle type using the class constant.

📋 What You'll Learn

Create a class named Vehicle.

Inside the class, define constants CAR_WHEELS with value 4 and MOTORCYCLE_WHEELS with value 2.

Outside the class, print the value of the constant CAR_WHEELS using the class name.

💡 Why This Matters

🌍 Real World

Constants in classes help keep fixed values organized and easy to maintain, like fixed settings or limits in a program.

💼 Career

Understanding class constants is important for writing clean, maintainable code in PHP, which is widely used in web development jobs.

1

Create the Vehicle class with constants

Create a class called Vehicle with two constants: CAR_WHEELS set to 4 and MOTORCYCLE_WHEELS set to 2.

PHP

<?php

// Create class Vehicle with constants CAR_WHEELS and MOTORCYCLE_WHEELS
// Your code here

Need a hint?

Use the const keyword inside the class to define constants.

2

Add a variable to hold the vehicle type

Create a variable called vehicleType and set it to the string 'CAR_WHEELS'.

PHP

<?php

class Vehicle {
    const CAR_WHEELS = 4;
    const MOTORCYCLE_WHEELS = 2;
}

// Create variable vehicleType and set it to 'CAR_WHEELS'
// Your code here

Need a hint?

Use a simple variable assignment with the exact string 'CAR_WHEELS'.

3

Access the constant using the variable

Create a variable called wheels and set it to the value of the constant in Vehicle class using the variable vehicleType. Use Vehicle::${vehicleType} syntax.

PHP

<?php

class Vehicle {
    const CAR_WHEELS = 4;
    const MOTORCYCLE_WHEELS = 2;
}

$vehicleType = 'CAR_WHEELS';

// Create variable wheels and set it to Vehicle::${vehicleType}
// Your code here

Need a hint?

Use the constant() function to access a class constant dynamically.

4

Print the number of wheels

Print the value of the variable wheels using echo.

PHP

<?php

class Vehicle {
    const CAR_WHEELS = 4;
    const MOTORCYCLE_WHEELS = 2;
}

$vehicleType = 'CAR_WHEELS';
$wheels = constant('Vehicle::' . $vehicleType);

// Print the value of wheels
// Your code here

Need a hint?

Use echo $wheels; to display the number of wheels.