First-class callable syntax in PHP - Mini Project: Build & Apply

Using First-class Callable Syntax in PHP

📖 Scenario: Imagine you are building a simple PHP program that processes a list of numbers by applying a function to each number. You want to use PHP's first-class callable syntax to pass functions easily.

🎯 Goal: You will create a list of numbers, define a function to double a number, use first-class callable syntax to apply this function to each number, and then print the results.

📋 What You'll Learn

Create an array called numbers with the values 1, 2, 3, 4, 5.

Create a function called double that takes one parameter and returns its value multiplied by 2.

Create a variable called doubleFunc that stores the first-class callable syntax for the double function.

Use array_map with doubleFunc to create a new array called doubledNumbers.

Print the doubledNumbers array using print_r.

💡 Why This Matters

🌍 Real World

First-class callable syntax helps you pass functions around easily, making your code cleaner and more flexible when processing data.

💼 Career

Understanding first-class callables is useful for PHP developers working on modern codebases, especially when using functional programming techniques or frameworks.

1

Create the numbers array

Create an array called numbers with the values 1, 2, 3, 4, 5.

PHP

# Create the array called numbers with values 1, 2, 3, 4, 5
# Your code here

Need a hint?

Use square brackets [] to create an array in PHP.

2

Define the doubling function

Create a function called double that takes one parameter $n and returns $n * 2.

PHP

<?php
$numbers = [1, 2, 3, 4, 5];

// Define the function double
# Your code here

Need a hint?

Define a function using the function keyword and return the doubled value.

3

Create the first-class callable variable

Create a variable called doubleFunc that stores the first-class callable syntax for the double function using double(...).

PHP

<?php
$numbers = [1, 2, 3, 4, 5];

function double($n) {
    return $n * 2;
}

// Store the first-class callable for double in doubleFunc
# Your code here

Need a hint?

Use double(...) to get the first-class callable and assign it to $doubleFunc.

4

Apply the function and print results

Use array_map with $doubleFunc and $numbers to create a new array called doubledNumbers. Then print doubledNumbers using print_r.

PHP

<?php
$numbers = [1, 2, 3, 4, 5];

function double($n) {
    return $n * 2;
}

$doubleFunc = double(...);

// Use array_map with doubleFunc and numbers to create doubledNumbers
// Print doubledNumbers
# Your code here

Need a hint?

Use array_map($doubleFunc, $numbers) to apply the function to each number.