exercises and solutions

Function exercises

Function exercises should make inputs, outputs, and failure behaviour explicit. Prefer a returned value that callers can use or test; print inside a function only when output is the function's responsibility.

Practical Example

PHP example

<?php

declare(strict_types=1);

function lineTotal(int $pricePence, int $quantity): int
{
    return $pricePence * $quantity;
}

echo lineTotal(499, 3) . PHP_EOL;

// Prints:
// 1497

Function exercises should ask learners to name inputs, return a value, and keep printing outside the function unless the function's job is output.

Extend exercises with a guard or type decision once the basic calculation works. A junior developer should be able to explain which layer rejects invalid input.

Practice

Write A Safe Line-Total Function

Show solution

Validate the quantity inside the function, throw InvalidArgumentException below one, and return $pricePence * $quantity. Printing lineTotal(499, 3) should produce 1497.

Keeping output outside the function makes the calculation easier to reuse and test.

Normalise A Product Name

Show solution

Trim first, reject '' with InvalidArgumentException, then return ucwords(strtolower($name)). Printing the result for " desk lamp " should produce Desk Lamp.

The guard belongs after trimming because whitespace-only input is not a useful product name.