Algorithm to get all possible string combinations from array up to certain length

Question

What is the best algorithm to get all possible string combinations from a given array with a minimum & maximum length value.

Note: This adds complexity since the

Answer 1

Accumulative set product for k times with a set S which is empty initially will produce all permutations up to k-long, with n = |S| ..

Time: O(kn^2)

Space: O(kn^2)

// Enumerate all permutations, PHP
// by Khaled A Khunaifer, 25/3/2013

function setProduct($a, $b)
{
    $arr = array();

    foreach ($a as $s)
    {
        foreach ($b as $t)
        {
            $arr[] = $s . $t;
        }
    }

    return $arr;
}

function enumerate ($arrary, $maxLen)
{
    $enumeration = array();

    for (var $i = 1; $i <= $maxLen; $i++)
    {
        $enumeration += setProduct($enumeration, $array);
    }
}