阶乘计算器返回INF值作为结果

下面的函数返回INF作为结果。我猜这是因为数字太大了，但我该怎么解决呢?

class Factoriel {
public function calculate() {
    if(func_num_args() != 1)
        throw new Exception ("Invalid arguments count for method calculate!");
    if(($n = (int)func_get_arg(0)) <= 0)
        throw new Exception ("Invalid argument supplied for method calculate!");
    $result = 1;
    foreach(range(1, $n) as $current)
        $result = $this->multiply ($result, $current);
    return $result;
}
private function multiply($left, $right) {
    return $left * $right;
   }
}
$factoriel = new Factoriel();
echo $factoriel->calculate(1500);