How do I store the results of this recursive function?

Question

I have the following PHP code which works out the possible combinations from a set of arrays:

function showCombinations($string, $traits, $i){

    if($i >= count($traits)){

        echo trim($string) . '<br>';

    }else{

        foreach($traits[$i] as $trait){
            showCombinations("$string$trait", $traits, $i + 1);
        }

    }

}

$traits = array(
            array('1','2'),
            array('1','2','3'),
            array('1','2','3')
            );

showCombinations('', $traits, 0);

However, my problem is that I need to store the results in an array for processing later rather than just print them out but I can't see how this can be done without using a global variable.

Does anyone know of an alternative way to achieve something similar or modify this to give me results I can use?

Answer 1

Return them. Make showCombinations() return a list of items. In the first case you only return one item, in the other recursive case you return a list with all the returned lists merged. For example:

function showCombinations(...) {
    $result = array();
    if (...) {
        $result[] = $item;
    }
    else {
        foreach (...) {
            $result = array_merge($result, showCombinations(...));
        }
    }
    return $result;
}

Answer 2

In addition to the other answers, you could pass the address of an array around inside your function, but honestly this isn't nearly the best way to do it.