Loose.php

<?php
function Loose(?array $foo) : ?array
{
    $localScoped = null;
    if ($foo !== null) {
        foreach ($foo as $bar) {
            $localScoped[] = $bar->stuff();
        }
    }

    return $localScoped;
}

function LooseCallee(?array $other) : ?array
{
    $localScoped = null;
    if ($other !== null) {
        foreach ($other as $bar) {
            $localScoped[] = $bar->stuff();
        }
    }

    return $localScoped;
}

Tight.php

<?php

function tight(array $foo) : array
{
    $localScoped = [];
    foreach ($foo as $bar) {
        $localScoped[] = $bar->stuff();
    }

    return $localScoped;
}

function tightCallee(array $resultSet) : array
{
    $localScoped = [];
    foreach ($resultSet as $bar) {
        $localScoped[] = $bar->stuff();
    }

    return $localScoped;
}