Interview Question for Software Development Engineer at Amazon.com:

function answer($num)
    {
        $index = 0;
        $highest = $num[0];
        while($index != count($num))
        {
            if($hash[$num[$index]])
                $hash[$num[$index]] ++;
            else
                $hash[$num[$index]] = 1;
            if($hash[$num[$index]]>$hash[$highest])
                $highest = $num[$index];
            $index ++;
        }
        return $hash[$highest] * $highest;
    }