Transforming with 'array_map'

Part of the Logic & Flow section of Coddy's PHP journey — lesson 39 of 68.

The array_map() function is a powerful tool that transforms every element in an array by applying a callback function to each one. Unlike functions that modify the original array, array_map() creates and returns a completely new array with the transformed values.

The basic syntax requires two parameters: first, the callback function you want to apply, and second, the array you want to transform. PHP has many built-in functions that work perfectly as callbacks with array_map().

<?php
$names = ["alice", "bob", "charlie"];
$uppercaseNames = array_map("strtoupper", $names);
// Result: ["ALICE", "BOB", "CHARLIE"]
?>

In this example, strtoupper is applied to each element in the $names array. The original array remains unchanged, while $uppercaseNames contains the transformed results. This makes array_map() ideal when you need to process data without losing the original values.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Challenge

Easy

You will receive two inputs: a comma-separated list of product prices and a discount percentage. The first input contains prices as a string in the format 19.99,25.50,12.75,8.00, and the second input is the discount percentage as a number (example: 15).

Read both inputs, convert the comma-separated prices into an array of numbers, apply the discount percentage to each price using array_map() with the built-in floatval function for conversion and a calculation for the discount, and print each discounted price on a separate line, rounded to 2 decimal places.

To calculate the discounted price: multiply the original price by (100 - discount) / 100.

Input format:

First line: Comma-separated product prices (example: 19.99,25.50,12.75,8.00)
Second line: Discount percentage as a number (example: 15)

Expected output: Each discounted price printed on a separate line, rounded to 2 decimal places (example: 16.99, 21.68, 10.84, 6.80)

Cheat sheet

The array_map() function transforms every element in an array by applying a callback function to each one. It creates and returns a new array with the transformed values, leaving the original array unchanged.

Basic syntax with built-in function:

<?php
$names = ["alice", "bob", "charlie"];
$uppercaseNames = array_map("strtoupper", $names);
// Result: ["ALICE", "BOB", "CHARLIE"]
?>

The function takes two parameters: the callback function and the array to transform. You can use built-in PHP functions or anonymous functions as callbacks.

Try it yourself

<?php
// Read input
$prices_input = trim(fgets(STDIN));
$discount = floatval(fgets(STDIN));

// Convert comma-separated prices to array
$prices = explode(',', $prices_input);

// TODO: Write your code below
// Use array_map() to apply the discount to each price


// Output each discounted price on a separate line

?>

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.