PHP 2D Array output all combinations

Question

Hi there,

I've had this problem bending my mind for a while now (head cold doesn't help either!), basically I have a PHP array which looks like this example:

$array[0][0] = 'apples';
$array[0][1] = 'pears';
$array[0][2] = 'oranges';

$array[1][0] = 'steve';
$array[1][1] = 'bob';

And I would like to be able to produce from this a table with every possible combination of these, but without repeating any combinations (regardless of their position), so for example this would output

Array 0            Array 1
apples             steve
apples             bob
pears              steve
pears              bob

But I would like for this to be able to work with as many different arrays as possible.

Many thanks!

Answer 1

this is called "cartesian product", php man page on arrays http://www.theserverpages.com/php/manual/en/ref.array.php shows some implementations (in comments).

and here's yet another one:

function array_cartesian() {
    $_ = func_get_args();
    if(count($_) == 0)
        return array(array());
    $a = array_shift($_);
    $c = call_user_func_array(__FUNCTION__, $_);
    $r = array();
    foreach($a as $v)
        foreach($c as $p)
            $r[] = array_merge(array($v), $p);
    return $r;
}

$cross = array_cartesian(
    array('apples', 'pears',  'oranges'),
    array('steve', 'bob')
);

print_r($cross);

Answer 2

In MySQL database in would be like this:

SELECT *
FROM `options`, `groups`

That's all :)

Answer 3

This works I think - although after writing it I realised it's pretty similar to what stereofrog has put, but it does give you an array in the format requested. Sorry for the poor variable naming.

$output = array();
combinations($array, $output);
print_r($output);

function combinations ($array, & $output, $index = 0, $p = array()) {
    foreach ( $array[$index] as $i => $name ) {
        $copy = $p;
        $copy[] = $name;
        $subIndex = $index + 1;
        if (isset( $array[$subIndex])) {
            combinations ($array, $output, $subIndex, $copy);
        } else {
            foreach ($copy as $index => $name) {
                if ( !isset($output[$index])) {
                    $output[$index] = array();   
                }
                $output[$index][] = $name;   
            }
        }
    }
}