PHP make combination array

index.php

function getCombination($input, $carry, &$result, $maxLength = null)
    {
        $maxLength = $maxLength ?: count($input);
        $oldCarry = $carry;
        foreach ($input as $index => $i) {
            $carry[] = $i;
            if (count($carry) <= $maxLength) {
                $result[] = $carry;
            }
            getCombination(array_slice($input, $index + 1), $carry, $result, $maxLength);
            $carry = $oldCarry;
        }
    }