PHP中布尔值的所有组合

Question

Related to Generating all the combinations of a set of boolean variables in Haskell and various other questions of the type.

I have a bunch of toggle switches in a database and want to get a list of all possible settings. The number of switches can change, specifically, users can add or remove.

I can get them into an array like

$switches = array('aaa', 'bbb', 'ccc');

and I would like to generate all possibilities, i.e. something like:

$states = array(
array('aaa' => false, 'bbb' => false, 'ccc' => false),
array('aaa' => false, 'bbb' => false, 'ccc' => true),
array('aaa' => false, 'bbb' => true, 'ccc' => false),
array('aaa' => false, 'bbb' => true, 'ccc' => true),
...
);

I don't particularily care in which order the result set is.

What's an elegant way to generate that?

Answer 1

Dunno if it's elegant, but for example use array_reduce with a callback:

$a = ['a', 'b', 'c'];
$states = array_reduce($a, function ($t, $v) {
    $newt = [];
    if (empty($t)) {
        $newt = [
            [$v => false],
            [$v => true],
        ];
    } else {
        foreach ($t as $item) {
            $newt[] = array_merge($item, [$v => false]);
            $newt[] = array_merge($item, [$v => true]);
        }
    }

    return $newt;
}, []);
var_dump($states);