JuniorTheoryCommon

What does the program print?

PHP

<?php

$prices = [10, 20, 30];
$withTax = array_map(fn($p) => $p * 1.1, $prices);
$total = array_reduce($prices, fn($sum, $p) => $sum + $p, 0);
echo count($withTax), ' ', $total, ' ', $prices[0], "\n";

3 60 10

Expecting array_map to change $prices: it returns a new array and leaves the original as it was, so $prices[0] is still 10.
Expecting $sum to start from 0 on every call: array_reduce passes what one call returns into the next one, starting from its third argument.

What does array_reduce return for an empty array when no initial value is given?
How would you get the same total with one built-in function?

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JuniorTheoryCommon

What does the program print?

PHP

<?php

$prices = [10, 20, 30];
$withTax = array_map(fn($p) => $p * 1.1, $prices);
$total = array_reduce($prices, fn($sum, $p) => $sum + $p, 0);
echo count($withTax), ' ', $total, ' ', $prices[0], "\n";

3 60 10

Expecting array_map to change $prices: it returns a new array and leaves the original as it was, so $prices[0] is still 10.
Expecting $sum to start from 0 on every call: array_reduce passes what one call returns into the next one, starting from its third argument.

What does array_reduce return for an empty array when no initial value is given?
How would you get the same total with one built-in function?

Back to questions Open topic in roadmap →Answer it yourself — Quiz