PHP Time and date

PHP provides a large number of built-in functions that enable developers to work on time, greatly improving productivity.

Describes some common PHP date and time functions and the processing of dates and times.

Frequently used date and time processing functions

function	Description
Checkdate	Validates the time function. Infers whether the time is valid, returns true correctly, otherwise returns false
Date_default_timezone_get	Gets the default time zone used by the script datetime function
Date_default_timezone_set	Set the default time zone for datetime functions
Date	Format a local time/date
GetDate	Get Date/Time information
Gettimeofday	Get current time
LocalTime	Get local time
Microtime	Returns the current timestamp and the number of microseconds
Mktime	Get a Unix timestamp
Strtotime	Parse the date-time descriptive narrative of any English text into a UNIX timestamp
Time	Returns the current UNIX timestamp

System Time zone settings

During the learning process, it was found that the time obtained through the date () function is different from the local time, because PHP5 has rewritten the date () function, so that the current datetime function is 8 hours less than the system time.

The default setting in the PHP language is the standard GMT (that is, the zero zone). There are two ways to change the time zone settings in the PHP language:
1. Change the settings in the php.ini file to find [date], date.timezone = option, change the item to Date.timezone=asia/hong_kong, and then start Apacheserver again.
2. In the application, use the time-date function before adding for example the following function:
Date_default_timezone_set ("Asia/hong_kong"); once set, the date () function is ready to use and no more time-lag problems occur.

Unix time stamp

Timestamps are the creation, alteration, and access times in file properties. Digital time stamp service, DTS, is one of the Web site security services projects that provide security for the date and time information of electronic files.

A timestamp is a document that has been encrypted and formed after it has been created. It consists of 3 parts:
2 files that need to be timestamp are encrypted with a hash code to form a digest.
2 DTS accepts the date and time information for the file.
2 Encryption of the accepted DTS files.
The digital time is added by the Authentication unit DTS. The time that DTS received the file is based on. The function of time stamp is to convert the value of time into an encrypted value by other encryption method, and the value of encryption will change after time change.

The advantage of time stamp is: The change of encryption value to prevent the value is stolen after illegal reuse, also played the role of encryption. Timestamps are mainly dependent on time and produce a unique value for a specified period of time.

Mktime () function

Grammar:
int mktime (int hour, int minute, int month, int day, int year, int [IS_DST])

number	say
Hour	hours
minute	minutes
second	seconds (within one minute)
month	Number of months
Day	days
Year	Number of years
Is_dst	Parameters is_dst in daylight saving time can be set to 1. Set to 0 if not determined if daylight saving time is set to 1 (default)

Note: A valid timestamp typically ranges from GMT December 13, 1901 20:45:54~2038 January 19 03:13:07 (this range conforms to the minimum and maximum values of 32-bit signed integers). This range is limited in Windows systems from January 1, 1970 ~2038 January 19.

Date () function

Date (string format,int timestamp)
The function returns the number of timestamp strings that are generated in accordance with the specified format. The parameter timestamp is optional, assuming omitted, the current time is used.

The format parameter allows the developer to output the time and date in the form it specifies.
Date_default_timezone_set (PRC); Set the GMT.

Example of a

format character	description	return value
Day	---	---
D	The day ordinal of a month with a leading zero 2-digit number	to
D	Day of the week, text representation, 3 letters	Mon to Sun
J	The day ordinal of the month. No leading zeros	1 to
l(lowercase letter of "L")	Day of the week, full text format	Sunday to Saturday
N	ISO-8601 format number represents the day of the week (PHP 5.1.0 new Plus)	1(for Monday) to 7(= Sunday)
S	English suffix, 2 characters, after the number of days per month	St,nd. Rd or th. Can be used with J .
W	Day of the week, numbers indicate	0(for Sunday) to 6(= Saturday)
Z	The day ordinal of the year	0 to 365
Week	---	---
W	Week of the ISO-8601 format year, starting from Monday (PHP 4.1.0 New)	For example: (42nd week of the year)
Month	---	---
F	Month. Complete text format, such as January or March	January to December
M	A number represents the month, with a leading zero	to
M	Three letter abbreviation for month	Jan to Dec
N	The month represented by the number. No leading zeros	1 to
T	The number of days that a given month should be	from
Years	---	---
L	Whether it is a leap year	A leap year is assumed to be 1, otherwise 0
O	ISO-8601 format year number. This is the same value as Y . Only if the number of weeks (W) of the ISO is assumed to belong to the previous or next year, then that year. (PHP 5.1.0 new addition)	Examples: 1999 or 2003
Y	4-digit year in full representation	For example:1999 or 2003
Y	Year 2-digit representation	For example :
Time	---	---
A	Lowercase morning and afternoon values	am or pm
A	Uppercase morning and afternoon values	AM or PM
B	Swatch Internet Standard Time	to 999
G	Hours, 12-hour format, no leading zeros	1 to
G	Hours. 24-hour format. No leading zeros	0 to
H	Hours, 12-hour format, with leading zeros	to
H	Hours, 24-hour format, with leading zeros	From xx to
I	Number of minutes with leading zeros	From xx to >
S	Number of seconds. With leading zeros	From xx to >
U	Milliseconds (PHP 5.2.2 new Plus). It is important to note that the date () function always returns 000000 because it accepts only integer parameters. and Datetime::format () only supports milliseconds.	Demo Sample: 654321
Time	---	---
E	Time zone ID (PHP 5.1.0 new addition)	For example:UTC,GMT,atlantic/azores
I	Whether it is daylight saving time	Let's say daylight saving time is 1, otherwise 0
O	Hours of difference from GMT	For example:+0200
P	The difference from Greenwich mean GMT (GMT). Colon separated between hours and minutes (PHP 5.1.3 New addition)	For example:+02:00
T	The time zone in which this machine resides	For example:EST,MDT("translator note" in Windows for the full text format, such as "Eastern Standard Time", the Chinese version will show "Chinese standards").
Z	The number of seconds of the slack offset. The time zone offset in the west of UTC is always negative, and the time zone offset to the east of UTC is always positive.	-43200 to 43200
Full Date/Time	---	---
C	Date in ISO 8601 format (PHP 5 new)	2004-02-12t15:19:21+00:00
R	Date in RFC 822 format	For example:Thu, Dec 16:01:07 +0200
U	The number of seconds since the Unix era (January 1 1970 00:00:00 GMT) started	See Time ()

GETDATE () function

The function returns the DateTime information in the form of an array, assuming that there is no timestamp, whichever is the current time.

Element	Description
Seconds	Seconds. return value 0~59
Minutes	Minutes with a return value of 0~59
Hours	Hours. The return value is 0~23
Mday	The day ordinal of the month. The return value is 1~31
Wday	The first day of the week, the return value is 0 (Sunday) to (Saturday)
Mon	Month number, return value is 1~12
Year	4-digit full year, return value plus 2000 or 2008
Yday	The first day of the year, the return value 0~365
Weekday	The full text representation of the day of the week, with a return value of Sunday~saturday
Month	The full text representation of the month. The return value is January~december
0	Returns the number of seconds since the Unix era

Two times the size of a

In the actual development often encountered inferred two time size, PHP time is not able to directly to do the comparison. Therefore, the time is first output to the timestamp format. And then the comparison, which is often used to the method.

There are two functions that can do this, using the strtotime() function, which resolves a datetime descriptive narrative of whatever English text to a Unix timestamp. The syntax for this function is:
int Strtotime (string time, int now)
The function has two parameters. Assume that the format of the parameter time is absolute. The now parameter does not work, assuming that the format of the parameter time is relative. Then the corresponding time is provided by the reference now, assuming that no parameters are provided, the corresponding time is the current time.

Assume that parsing failed. then return-1.

Calculate the execution time of a page script

When browsing the site, search engines are often used. When searching for information. The attentive user will find out. At the bottom of the search results, there is usually a "search time for ...". Seconds "of the word. The microtime() function is used here to return the current UNIX timestamp and the number of microseconds. Returns a string formatted as msec sec, in which the SEC is the current Unix timestamp and msec is the number of microseconds.

The format of the function is:
String Microtime (void)

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PHP Time and date