PHP solution to strtotime('- x month') bug

When developing projects before, I encountered bugs when using strtotime("- 1 month"). The main reason is that the default time set by PHP is based on Greenwich Time Zone. There are two ways to solve this problem. , one is to modify the default time zone in php.ini, and the other is to set it in the program

Let’s talk about the first method first, modify the default time zone in php.ini

I use the wamp integrated environment, which I have been using before. I thought I was modifying the default time zone in bin/php/php5.5.12, but no matter how I modified it, the time in the Greenwich Time Zone was still displayed, and no corresponding solution was found online. Later, I modified it in bin/apache/apache2.4.9 I found a php.ini file in /bin and set the time zone of the file to date.timezone = PRC. Then the time displayed on the page is the same as my system time.

The setting method is to modify the time zone in the php.ini file to the time in our region. For example, modifying date.timezone = PRC means setting the time to the time of the People's Republic of China, which is the current time of our system. Note: In order To make the time zone we set take effect, we need to remove the preceding ;.

The second method is to add date_default_timezone_set('PRC');

such as

date_default_timezone_set('PRC');//This sentence is used to eliminate the time difference
$date = date(" Y-m-d H:i:s");

echo $date; //Output

?>

This way we can output our current time.

Now there is another problem. When the time is 2016-03-31, when using the above method to obtain the time of the previous month, the time obtained is still 2016-03. The initial assumption is that this method is to search first The number of days in the previous month, and then subtract the number of days in the previous month using today's time.

There are several methods below that can help us achieve the desired results. For example, I want to return the month of last month:
echo date('Y-m', strtotime('midnight first day of -1 month'));
Or:
echo date('Y-m', strtotime(date('Y-m-01')) – 86400);

Or do the following processing in the program

date_default_timezone_set('Asia/Shanghai' );
$first_day_of_month = date('Y-m',time()) . '-01 00:00:01';
$t = strtotime($first_day_of_month);
print_r(array(

date('Y Year m month',$t),
date('Y year m month',strtotime('- 1 month',$t)),
date('Y year m month',strtotime('- 2 month', $t)),
));
?>

The principle of doing this is to separate the year and month of each month's time, and then add the day, hour, minute and second at the end, so when doing strtotime('- 1 month',$t) operation, the time of the previous month can be displayed.

Another note:

When using strtotime(date("Y-m-d h:i:s")) for time processing, the letters here are case-sensitive,

h is case-sensitive, The lowercase h outputs the hour in the time zone, 17 o'clock is 5 o'clock. The uppercase H outputs 17,

and the year y is case-sensitive, and the lowercase y outputs 13. The output of capital Y is 2013.