JuniorTheoryCommon

What does the program print?

PHP

<?php

function push(array $list, string $x)
{
    $list[] = $x;
    return count($list);
}

$cart = ['tea'];
$n = push($cart, 'milk');
echo $n, ' ', count($cart), "\n";

2 1

Expecting 2 2, as if an array were passed by reference: without & the parameter is a copy, so adding to $list leaves $cart as it was.
Expecting a function to be unable to change its parameter: it may, but the change stays in its own copy and is gone after the call.

How would you change push so that $cart itself gets the new element?
Why is passing a large array to a function cheap until the function writes to it?

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JuniorTheoryCommon

What does the program print?

PHP

<?php

function push(array $list, string $x)
{
    $list[] = $x;
    return count($list);
}

$cart = ['tea'];
$n = push($cart, 'milk');
echo $n, ' ', count($cart), "\n";

2 1

Expecting 2 2, as if an array were passed by reference: without & the parameter is a copy, so adding to $list leaves $cart as it was.
Expecting a function to be unable to change its parameter: it may, but the change stays in its own copy and is gone after the call.

How would you change push so that $cart itself gets the new element?
Why is passing a large array to a function cheap until the function writes to it?

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