PHP date and time operations

Date and time are usually used for display and conditional restrictions in programming languages. More specifically, you may want to display the time in a certain format, display the time in a certain time zone, get the time after one week, get the timestamp of the beginning of this week, convert the time in a certain format into another, etc. wait.

1. Display the current time

Use the date function, the format is date(format[, timestamp]), which accepts two parameters, The first parameter is a time format string, and the second parameter is a timestamp. The timestamp is optional. If not filled in, it will be the timestamp of the current time.

echo date('Y-m-d H:i:s');  // 2018-12-25 09:31:22

Like this, you can print out the current year, month, day, hour, minute and second. Of course, you can also print out the time in other formats depending on the format string:

echo date('l dS \of F Y h:i:s A');  // Tuesday 25th of December2018 09:34:54 AM

Explain what is used above Format characters:

Y Complete year, 4 digits

m Month with leading 0

d The day of the month, with a leading 0

H Hour in the 24-hour format, with a leading 0

i Minutes, with a leading 0

s Seconds, with leading 0

l The complete English version of the day of the week (note the lowercase L, not the uppercase i)

S ​​The suffix of the number of days in the month (may be st, nd, rd, th)

F The complete English of the month

h 12-hour hour, with leading 0

A Morning or afternoon (AM or PM)

This is just a list For some of them, you can check the official manual for more complete format characters.

2. Display the world in a certain time zone

For example, by setting the time zone, we can get the time in the United States:

date_default_timezone_set("America/New_York");
echo date('Y-m-d H:i:s');  // 2018-12-24 20:54:36

The above is the world of New York, USA. You can check the PHP documentation for the string required by the time zone. If it is illegal, a warning will be generated. At the same time, the time zone will not be set successfully, but the default time zone will be used.

3. Calculated time

For example, the time at the beginning of this week, the beginning of this month, the time after one week, etc., you can Use the strtotime function to do this for us.

strtotime(time[, now = time()]) can convert any string describing time and date into a unix timestamp. The first parameter is the description string, and the second parameter is used to calculate timestamp (defaults to the current timestamp). You can tell from the description that it is a very flexible function, but be aware that it is a function after all. It is not so smart that it can understand "any" string describing time. It still needs a specific format - especially in China. , don’t expect it to understand what “December 25, 2018” means. But it is still very powerful and can do all the functions described previously.

echo '下个星期的时间：' . date('Y-m-d H:i:s', strtotime('+1 week'));  // 下个星期的时间：2019-01-01 10:12:16
echo '本周开始时间：' . date('Y-m-d H:i:s', strtotime('this week Monday'));  // 本周开始时间：2018-12-24 00:00:00
echo '明天开始时间：' . date('Y-m-d 00:00:00', strtotime('+1 day'));  // 明天开始时间：2018-12-26 00:00:00
echo '1天2小时3分5秒之后的时间：' . date('Y-m-d H:i:s', strtotime('+1 day 2 hours 3 minutes 5 seconds'));  // 1天2小时3分5秒之后的时间：2018-12-26 12:24:15

4. Create a time based on specific values

If you know the year, month, day, hour, minute, and second of a certain time , if you want to use them to create a time, you can choose to splice them into a time string and then use strtotime to parse it, or in this case you can also use a more reliable method: mktime.

mktime(hour, minute, second, month, day, year) It should be noted that the order of parameters is not the same as our habits, which is: hour, minute, second, month, day, year

$time = mktime(3, 10, 15, 2, 15, 2014);
echo date('Y-m-d H:i:s', $time);  // 2014-02-15 03:10:15

5. Time operations of object types

php also supports time operations of object types

$date_obj = date_create();  // 创建一个DateTime对象
echo $date_obj->format('Y-m-d H:i:s');  // 2018-12-25 10:45:08
 
date_add($date_obj, date_interval_create_from_date_string("3 days"));  // 给对象增加3天
echo $date_obj->format('Y-m-d H:i:s');  // 2018-12-28 10:45:08
 
date_sub($date_obj, date_interval_create_from_date_string("2 days"));  // 给对象减少2天
echo $date_obj->format('Y-m-d H:i:s');  // 2018-12-26 10:45:08
 
echo '时区为：' . timezone_name_get(date_timezone_get($date_obj));  // 时区为：PRC （中国时区，获取时区并打印）

It is different from the procedural style, but it can be implemented The functions are actually quite similar.

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