JuniorTheoryCommon

What happens when you run this program?

PHP

<?php

function square(int $n): int
{
    return $n * $n;
}

echo square('4'), ' ', square(2.0), "\n";
echo square('four'), "\n";

16 4, then a TypeError for 'four'

Expecting a TypeError already on '4': without strict_types PHP converts a numeric string to int, so square('4') returns 16.
Expecting 'four' to become 0: a parameter typed int converts only a string that holds a number; any other string throws a TypeError at the call.

JuniorTheoryCommon

PHP

<?php

function square(int $n): int
{
    return $n * $n;
}

echo square('4'), ' ', square(2.0), "\n";
echo square('four'), "\n";

16 4, then a TypeError for 'four'

Expecting a TypeError already on '4': without strict_types PHP converts a numeric string to int, so square('4') returns 16.
Expecting 'four' to become 0: a parameter typed int converts only a string that holds a number; any other string throws a TypeError at the call.