cal_days_in_month() [function.cal-天数-月]：日期无效

Question

我想计算一个月的天数。它显示了这样的警告：

cal_days_in_month() [function.cal-days-in-month]: invalid date. 

有人能帮帮我吗。：

$numberofday = new DateTime($month);
$numberofday = cal_days_in_month(CAL_GREGORIAN, $month,$year1);
$Total=$length  x 24  x $numberofday ; 

Answer 1

cal_days_in_month()接受月份字段的整数值，请将月份转换为整数：

$month = "april";
$year1 = "2013";
$month = date('m', strtotime($month));

在使用函数之前。

$numberofday = cal_days_in_month(CAL_GREGORIAN, $month, $year1);

cal_days_in_month的替代方案

$month = "april";
$year1 = "2013";
$numberofday = date('t', strtotime("$year1-" . date("m",strtotime($month)) . "-01"));

另外：

$Total=$length  x 24  x $numberofday;

应该是：

$Total=$length * 24 * $numberofday;

Answer 2

你有'length'，它应该是$length吗？

Answer 3

$month = 4；

$year1 = 2013；

$numberofday = cal_days_in_month(CAL_GREGORIAN，$month，$year1)；

echo $numberofday；//30