我找到最高素因子的功能有什么问题？

function find_highest_prime_factor($n)
{
    for ($i = 2; $i <= $n; $i++) 
    {   
        if (bcmod($n, $i) == 0) //its a factor
        {
            return max($i, find_highest_prime_factor(bcdiv($n,$i)));
        }
    }
    if ($i == $n)
    {
        return $n; //it's prime if it made it through that loop
    }
}
function find_highest_prime_factor($n)
{
    fo