Constructor promotion in PHP - Mini Project: Build & Apply

Constructor Promotion in PHP

📖 Scenario: You are creating a simple PHP class to represent a book in a library system. Each book has a title, an author, and a number of pages.

🎯 Goal: Build a PHP class Book using constructor promotion to set the properties title, author, and pages. Then create an instance and display its details.

📋 What You'll Learn

Create a class called Book with three properties: title, author, and pages.

Use constructor promotion to initialize these properties in the constructor.

Create a variable called myBook that is an instance of Book with the title '1984', author 'George Orwell', and pages 328.

Print the book details in the format: 'Title: 1984, Author: George Orwell, Pages: 328'.

💡 Why This Matters

🌍 Real World

Constructor promotion helps write cleaner and shorter code when creating classes with many properties, common in real-world PHP applications like content management systems or APIs.

💼 Career

Understanding constructor promotion is useful for PHP developers to write modern, efficient, and readable code, which is valued in many web development jobs.

1

Create the Book class with promoted properties

Create a class called Book with a constructor that uses constructor promotion to declare and initialize the public properties title (string), author (string), and pages (int).

PHP

<?php

// Create the Book class with constructor promotion
# Your code here

Need a hint?

Use the syntax public function __construct(public string $title, public string $author, public int $pages) {} inside the class.

2

Create an instance of the Book class

Create a variable called myBook and assign it a new Book object with the title '1984', author 'George Orwell', and pages 328.

PHP

<?php

class Book {
    public function __construct(
        public string $title,
        public string $author,
        public int $pages
    ) {}
}

// Create an instance of Book called myBook
# Your code here

Need a hint?

Use $myBook = new Book('1984', 'George Orwell', 328); to create the object.

3

Access the properties of the Book instance

Use a print statement to display the book details in the format: 'Title: 1984, Author: George Orwell, Pages: 328' by accessing the title, author, and pages properties of myBook.

PHP

<?php

class Book {
    public function __construct(
        public string $title,
        public string $author,
        public int $pages
    ) {}
}

$myBook = new Book('1984', 'George Orwell', 328);

// Print the book details
# Your code here

Need a hint?

Use print("Title: {$myBook->title}, Author: {$myBook->author}, Pages: {$myBook->pages}"); to show the details.

4

Display the final output

Run the program and ensure it prints exactly: Title: 1984, Author: George Orwell, Pages: 328

PHP

title}, Author: {$myBook->author}, Pages: {$myBook->pages}");

// Run the program and check output
# Your code here

Need a hint?

Make sure your print statement matches the exact output including punctuation and spacing.