t 返回给定日期的月份天数（见 日期的文档 ）：

  $ a_date =2009-11-23; 
 echo date（Y-m-t，strtotime（$ a_date））; 
 

How can I get the last day of the month in PHP?

Given:

$a_date = "2009-11-23"

I want 2009-11-30; and given

$a_date = "2009-12-23"

I want 2009-12-31.

t returns the number of days in the month of a given date (see the docs for date):

$a_date = "2009-11-23";
echo date("Y-m-t", strtotime($a_date));