PHP自訂函數round_pad_zero 小數位四捨五入並補零

/**
* 小数位四舍五入并补零
* by bbs.it-home.org
*/
function round_pad_zero($num, $precision)
{
    if ($precision < 1) {
        return round($num, 0);
    }
    $r_num = round($num, $precision);
    $num_arr = explode('.', "$r_num");
    if (count($num_arr) == 1) {
        return "$r_num" . '.' . str_repeat('0', $precision);
    }
    $point_str = "$num_arr[1]";
    if (strlen($point_str) < $precision) {
        $point_str = str_pad($point_str, $precision, '0');
    }
    return $num_arr[0] . '.' . $point_str;
}
//调用示例
echo round_pad_zero(3223342.506, 4);