PHP中的日期算术

Is there a PHP function I can use to do something like the following:

• Get the date 6 months ago (e.g. now - 6 months)?
• Get the date 2 years from now (e.g. now + 2 years)?

Yes, there is: strtotime():

1. 6 months ago: strtotime("-6 months");
2. 2 years: strtotime("+2 years");

These will return Unix timestamps. So you might want to put the result into date() or localtime() or gmtime().

Please do not try to subtract 6 months or add 2 years of seconds to time(). This does not take into account things like daylight saving or leap seconds and still gives you a value in seconds which is unlikely to be the precision you need. Let the library functions do it.

Like this:

$date6monthsago = strtotime('-6 months');
$date2year = strtotime('+2 year');

Choose according to your use following code..

echo date('m/d/Y',strtotime("-6 months")); //ago 6month o/p 05/23/2011 
echo date('d-m-Y',strtotime("6 months"));  //comming 6month o/p 23-05-2012
echo date('m.d.Y',strtotime("+2 years"));  //comming year o/p 11.23.2013

http://de2.php.net/manual/en/datetime.add.php and similar "new" methods may also be your friend.