binary sets

bin-sets.php

<?php

function sets_of($list) {
    $sets = [];
    $total = 1 << count($list);
    for ($i = 0; $i < $total; $i++) {
        $sub = [];
        foreach ($list as $j => $val) {
            if ($i & (1 << $j)) {
                $sub[] = $val;
            }
        }
        $sets[] = $sub;
    }
    return $sets;
}

print_r(sets_of([1, 2, 3, 4]));
print_r(sets_of(["a", "b", "c", "d"]));