<?php
$regions = [
'int' => 1,
'nl' => 2,
'be' => 4,
'us' => 8,
'as' => 16,
'za' => 32,
];
for ($i = 0; $i < (1 << count($regions)); $i++)
array_walk(@array_filter($regions, function ($x) use ($i) { return $x & $i; }),
function ($x, $region) use (&$list) { isset($list[$region]) and $list[$region] .= ","; $list[$region] .= $x; }
);
var_dump($list);
preferences:
44.13 ms | 402 KiB | 5 Q