Question

I’m having trouble creating the recipes for a multi-variate test. For example, if I wanted to test a combination of outfits and I had 3 different hats, shirts, and pants. I want to list every possible combination of them without duplicates. This is my thought process so far:

// outfit #1
$outfit[0][0] = "hat A ";
$outfit[0][1] = "shirt A ";
$outfit[0][2] = "pants A ";

// outfit #2
$outfit[0][0] = "hat B ";
$outfit[0][1] = "shirt B ";
$outfit[0][2] = "pants B ";

// outfit #3
$outfit[0][0] = "hat C ";
$outfit[0][1] = "shirt C ";
$outfit[0][2] = "pants C ";

function recipeMaker()
{
    $i = 0;
    $j = 0;
    foreach ($outfit as $outfit_2)
    {
          foreach ($outfit_2 as $outfit_3)
          {
              ...some magic here...
              recipe[$i][$j] = ...something goes here...
              $j++;
          }
     $i++;
    }    
} 

foreach ($recipe as $r)
{
    echo $r . "<br />";
}

Then it should output:

hat A shirt A pants A
hat B shirt A pants A
hat C shirt A pants A
hat A shirt B pants A
etc.

Answer 1

You could go down the route of nesting foreach loops, but what happens when you want to extend the outfit (e.g. add a list of ties)? Here’s a solution which outputs the combinations available from any number of collections:

class Combiner {
    protected $_collections;
    protected $_combinations;

    public function __construct() {
        $args = func_get_args();

        if (count(array_filter(array_map('is_array', $args))) !== func_num_args()) {
            throw new Exception('Can only pass array arguments');
        }

        $this->_collections = $args;
    }

    protected function _getBatch(array $batch, $index) {
        if ($index < count($this->_collections)) {
            foreach ($this->_collections[$index] as $element) {
                // get combinations of subsequent collections
                $this->_getBatch(array_merge($batch, array($element)), $index + 1);
            }
        } else {
            // got a full combination 
            $this->_combinations[] = $batch;
        }
    }

    public function getCombinations() {
        if (null === $this->_combinations) {
            $this->_getBatch(array(), 0);
        }

        return $this->_combinations;
    }
}

$hats = array('Hat A', 'Hat B', 'Hat C');
$shirts = array('Shirt A', 'Shirt B', 'Shirt C');
$pants = array('Pants A', 'Pants B', 'Pants C');

$combiner = new Combiner($hats, $shirts, $pants);
var_dump($combiner->getCombinations());

It moves along the list of types and picks one (say Hat A) then recursively builds the combinations of the rest of the types that go with that item. To add a new type it’s as simple as passing another argument to the constructor.