Getting all possible combinations of N items in X Groups.

Question

I have a list of Groups that can vary in number, with Items in these groups that also vary in number. I've been racking my head over a way to get all possible combinations of 1 Item from every Group.

Bonus: I also need all combinations of not having every items from a group.

I've seen and done what was mentioned before, but that requires knowing the number of groups to begin with.

To be more specific about what I'm doing, I would like to generate products with exact pricing based off product options. Here's an example list:

So it would generate products like:

UV Coating, Qty 500, Color 4:0
UV Coating, Qty 500, Color 4:1
etc...

Each of these Groups has an ID, and each item has a Group_Item_ID. So I can put them in an array such as:

$selections[1][...]  // 1 = Coating
$selections[2][...]  // 2 = Quantity
// ... = all selected Items in group

Hope I explained it well enough. I'm just not able to wrap my head around how to do this when the number of Groups are variable also.

Here's an example array for the groups and their items:

Array
(
[0] => Array
    (
        [0] => 2
        [1] => 3
    )

[1] => Array
    (
        [0] => 10
        [1] => 11
        [2] => 12
    )

[2] => Array
    (
        [0] => 16
        [1] => 17
    )

[3] => Array
    (
        [0] => 19
        [1] => 20
    )
)

Answer 1

Try this:

function c($groups, $prefix='')
{
    $result = array();
    $group = array_shift($groups);
    foreach($group as $selected) {
        if($groups) {
            $result = array_merge($result, c($groups, $prefix . $selected. ' '));
        } else {
            $result[] = $prefix . $selected;
        }
    }
    return $result;
}