Collection of date processing methods in PHP_PHP tutorial-PHP Tutorial-php.cn

This article contains the following contents:
1. Get the current date and time - how many ways do we have?
2. Change the way date is displayed - the display format of date and time
3. Convert the current date to Unix timestamp value
4. Change the date
a. Add time
b . Subtract time
c. Find the interval between two dates
5. Add DateAdd function to PHP
6. Add DateDiff function to PHP

** Get the current date and Time

In Unix, time is expressed by calculating the number of seconds that have passed since 0:00 on January 1, 1970. This is called a UNIX timestamp (Unix Epoch).
If we have such a piece of code:
?
echo time();
?
will return the value 958905820
The time at this time is May 21, 2000. Hours 43 minutes.
You might say this is pretty good. When this doesn't help me at all, or only a little. In PHP, all date processing functions must use the timestamp value returned by time(). At the same time, since PHP uses the same timestamp value in both Unix and Windows systems, this allows you to port it between different systems without modifying the code. Another benefit is that the time() function returns an integer, which you can store in the database as an integer field or a text field without having to use a special date/time field.
You have a basic understanding of the Unix timestamp value, now let us show its practical use.

Change the way date is displayed - the display format of date and time

PHP provides two methods to convert Unix timestamp values into useful data. The first is the date() function. This function takes two parameters - the first string is used to set the format you wish to return, and the second is the Unix timestamp value.
Format string uses some simple special formatting characters to display the date and time in the format you want to see. Suppose you want the date to be displayed in the format "18h01 Sunday 21 May".
We need to use a special formatting character for each part of the string, which you can find from the date and time function library in the PHP manual. There are a lot of such special formatting characters. They represent the day of the week, the English name of the month, the year represented by 2 or 4 digits, whether it is morning (AM) or afternoon (PM) and others. The special characters we need for this example are:
'H' - the hour in the 24-hour clock
'i' - the minute
'l' - the full English name of the day of the week
'd' - The day of this month
'F' - the full English name of the month
So our format string is "Hhi l d F", and the PHP code is:
?
echo date ( "Hhi l d F" ,time());
?
When we execute this code, we find that the result we get is:
180609 Sunday 21 May
This result looks like Something strange. Let's check the PHP manual again. It turns out that 'h' represents the hour in the 12-hour clock. This once again proves the truth: "The computer only does what you tell it to do, not what you want it to do."We have two options. The first one is to use the escape character "" before h:
echo date ("Hhi l d F", time());
We get this result:
18h12 Sunday 21 May
This is exactly what we want. But if we need to include a date and time in a very complex sentence, do we need to use escape characters for each character?
The answer is of course no. We use another function strftime().
strftime() has two benefits. The first benefit is beyond the scope of this article - if you use the setlocale() function, you can get the name of the month in the corresponding language through strftime. An additional benefit is that you can include special date and time formatting characters in your strings. This also means that whether or not you want to learn all the special formatting characters for the date() function, you have to learn a whole different set of formatting characters.
Strftime() works no differently than date(), except that the special formatting character must be preceded by a percent sign %. If you use the strftime() function, the code of the previous example is as follows:
?
echo strftime ("%Hh%M %A %d %b", time());
?
The result is :
18h24 Sunday 21 May
This may seem oversimplified, but consider if you need to display "Today is Sunday 21 May 2000. The time is somewhere close to 18h24." I would like to use The date() function is undoubtedly annoying.
At the beginning, I mentioned that we have two ways to get useful data from Unix timestamp values. We just learned about date() and strftime(). Another getdate(). This function only requires a Unix timestamp value as a parameter, and the return value of the function is an array of date and time.
The following is an example:
?
$date_time_array = getdate (time());
echo $date_time_array[ "weekday"];
?
The returned result is:
Sunday
Except "weekday", the other parts of the array are:
"seconds" - seconds
"minutes" - minutes
"hours" - hours
"mday" - this Day of the month
"wday" - day of the week (number)
"mon" - month (number)
"year" - year
"yday" - r this year The day of the month (number)
"month" - the full name of the month
We can now get an easily identifiable date and time. What about others?

**Convert the current date to a Unix timestamp value

Usually you have to deal with data in some date or time format. Open an Access database of M$. All dates are stored in the format of YYYY/MM/DD. Adding the current date is 2000/05/27. The Mktime() function can convert a time into a Unix timestamp value.
The format of the function is: int mktime(int hour, int minute, int second, int month, int day, int year, int [is_dst]);
You must provide hours, minutes, and seconds from left to right , month, day and year. The last parameter is used to specify whether you are in daylight saving time, this parameter is optional, so we will ignore it.
The code is as follows:
?
echo mktime (0, 0,0,5, 27,2000);
?
Since we don’t know the hours, minutes and seconds at the same time, these parameters must be filled in, I set it to 0. Setting to 0 means the time is midnight.
?
$access_date = "2000/05/27";
//The explode() function uses one string as a demarcation to explode another string.In this example $access_date is decomposed by the string "/"
$date_elements = explode("/" ,$access_date);
// At this time
// $date_elements[0] = 2000
// $date_elements[1] = 5
// $date_elements[2] = 27
echo mktime (0, 0,0 ,$date_elements [1], $date_elements[ 2],$date_elements [0] ; 🎜>// String from Access
$date_time_string = "2000/05/27 02:40:21 PM";
// Break the string into 3 parts - date, time and AM/PM
$dt_elements = explode(" " ,$date_time_string);
// Explosion date
$date_elements = explode("/" ,$dt_elements[ 0]);
// Explosion time
$time_elements = explode(":" ,$dt_elements[ 1]);
// If it is afternoon, we increase the time by 12 hours to get the 24-hour time
if ($dt_elements [2]== "PM") { $time_elements[ 0]+=12;}
// Output result
echo mktime ($time_elements [0], $time_elements[ 1], $time_elements[ 2], $date_elements[1 ], $date_elements[2], $date_elements[0]);
?

**Modification date

Sometimes we need to know what time it is 6 hours later, 35 days ago Date or how many seconds have passed since you last played Quake 3. We already know how to get a Unix timestamp value from a separate date and time using the mktime() function. What should we do if we need a Unix timestamp value other than the current date and time? Here are some exercises to help illustrate what we will do next.
As seen earlier, mktime() takes the following parameters: hours, minutes, seconds, months, days and years. Think about Section 2, the getdate() function can get these parameters for us.
?
//Put the current timestamp value into an array
$timestamp = time();
echo $timestamp;
echo "p";
$date_time_array = getdate( $timestamp);
// Use the mktime() function to regenerate the Unix timestamp value
$timestamp = mktime($date_time_array ["hours"], $date_time_array["minutes" ],$date_time_array[ "seconds"],$date_time_array ["mon"], $date_time_array["mday" ],$date_time_array[ "year"]);
echo $timestamp;
?
Looks a little surprising Confused. I'm going to use some variables to make the above program look easier to understand.
?
//Put the current timestamp value into an array
$timestamp = time();
echo $timestamp;
echo "p";
$date_time_array = getdate( $timestamp);
$hours = $date_time_array[ "hours"];
$minutes = $date_time_array["minutes"];
$seconds = $date_time_array[ "seconds"];
$month = $date_time_array["mon"];
$day = $date_time_array["mday"];
$year = $date_time_array["year"];
// Use mktime() The function regenerates the Unix timestamp value
$timestamp = mktime($hours ,$minutes, $seconds,$month ,$day,$year);
echo $timestamp;
?
Now we The timestamp value generated by getdate() is put into the corresponding name variable, so the code becomes relatively easy to read and understand. Now if we need to add 19 hours to the current time, we use $hours+19 instead of $hours in the mktime() function. mktime() will automatically move the time to the next day for us.
?
//Put the current timestamp value into an array
$timestamp = time();
echo strftime( "%Hh%M %A %d %b",$ timestamp);
echo "p";
$date_time_array = getdate($timestamp);
$hours = $date_time_array["hours"];
$minutes = $date_time_array["minutes"] ;
$seconds = $date_time_array["seconds"];
$month = $date_time_array["mon"];
$day = $date_time_array["mday"];
$year = $ date_time_array["year"];
// Use the mktime() function to regenerate the Unix timestamp value
// Add 19 hours
$timestamp = mktime($hours + 19, $minutes,$seconds, $month, $day,$year);
echo strftime( "%Hh%M %A %d %b",$timestamp);
echo "br~E after adding 19 hours";
?
After running, we get:
14h58 Saturday 03 Jun
09h58 Sunday 04 Jun
~E after adding 19 hours
The same goes for reducing time - you just need to reduce the value of the corresponding variable .
Getting the difference between two different time values is also very simple. All you need to do is convert the two time values into Unix timestamp values and then subtract the two. The difference between the two is the number of seconds between the two times. Other algorithms can quickly convert seconds to days, hours, minutes, and seconds.

**Add DateAdd function to PHP

As I said at the beginning of the article - the reason for writing this article is because I can't find an ASP-like DateDiff function in PHP. After introducing how PHP handles dates and times, let us transplant two functions commonly used in ASP to PHP. The first function is DateAdd.
According to the Vbscript documentation, the DateAdd(interval,number,date) function is defined as "Returns the date to which the specified time interval has been added."
Inetrval is a string expression representing the time interval to be added, such as minutes or days; number is a numerical expression representing the number of time intervals to be added; Date represents the date.
Interval (time interval string expression) can be any of the following values:
yyyy year
q Quarter
m Month
y Day of year
d Day
w Weekday Number of days in a week
ww Week of year
h Hour
n Minute
s Second
w, y and d have exactly the same effect , that is, add one day to the current date, add 3 months to q, and add 7 days to ww.
?
function DateAdd ($interval, $number, $date) {
$date_time_array = getdate($date);
$hours = $date_time_array["hours"];
$ minutes = $date_time_array["minutes"];
$seconds = $date_time_array["seconds"];
$month = $date_time_array["mon"];
$day = $date_time_array["mday" ];
$year = $date_time_array["year"];
switch ($interval) {
case "yyyy": $year +=$number; break;
case "q": $month +=($number*3); break;
case "m": $month +=$number; break;
case "y":
case "d":
case "w": $day+=$number; break;
case "ww": $day+=($number*7); break;
case "h": $hours+=$number; break;
case "n": $minutes+=$number; break;
case "s": $seconds+=$number; break;
}
$timestamp = mktime($hours,$minutes, $seconds ,$month ,$day, $year);
return $timestamp;}
?
We can save the above code as dateadd.inc file, and then run the following code:
?
include('dateadd.inc');
$temptime = time();
echo strftime( "%Hh%M %A %d %b",$temptime);
$temptime = DateAdd ("n" ,50,$temptime);
echo "p";
echo strftime( "%Hh%M %A %d %b",$temptime);
?
us You will get:
15h41 Saturday 03 Jun
16h31 Saturday 03 Jun
Add DateDiff function to PHP
Now that DateAdd is completed, what about DateDiff?
According to the documentation, the DateDiff(interval, date1, date2) function is defined as "returning the time interval between two dates".
The usage of the Intervals parameter is the same as that in the DateAdd function. In order to avoid excessive complexity, we decided to ignore other complex parameters in the DateDiff function in Vbscript, namely its two optional parameter variables [firstdayofweek[, firstweekofyear]] (they are used to determine whether the first day of the week is Sunday or Constants for Monday and the first week of the year, and we only allow intervals to have the following five values: "w" (week), "d" (day), "h" (hour), "n" (minute). and "s" (seconds).

Let's see what we can come up with: The following code is what we need:
?
Function DateDiff ($interval, $date1,$date2 ) {
// Get the number of seconds between two dates
$timedifference = $date2 - $date1;
switch ($interval) {
case "w": $retval = bcdiv( $timedifference ,604800); break;
case "d": $retval = bcdiv( $timedifference,86400); break;
case "h": $retval = bcdiv ($timedifference,3600); break;
case "n": $retval = bcdiv( $timedifference,60); break;
case "s": $retval = $timedifference; break;
}
return $retval;}
?
Save the above code as datediff.inc file, and then run the following code:
?
include('datediff.inc');
include('dateadd.inc') ;
$currenttime = time();
echo "Current time: ". strftime("%Hh%M %A %d %b" ,$currenttime)."br";
$newtime = DateAdd ("n",50 ,$currenttime);
echo "Time plus 50 minutes: ". strftime("%Hh%M %A %d %b" ,$newtime)."br";
$temptime = DateDiff ("n",$currenttime ,$newtime);
echo "Interval between two times: ".$temptime;
?
If everything goes well, you can see the following results:
Current time: 16h23 Saturday 03 Jun
Time plus 50 minutes: 17h13 Saturday 03 Jun
Interval between two times: 50
If you are running PHP on a Unix machine, you must compile PHP to support BC high precision function. You must download the BC library from the following address http://www.php.net/extra/number4.tar.gz, then unzip it to the root directory of PHP4, recompile PHP, and add --enable- when compiling. Options for bcmath. (See README.BCMATH in PHP4 for detailed instructions). The Windows version of PHP4 can directly use BC high-precision functions without any patching.
Now that you have the functions to handle dates and times, all that’s left is how to apply them to your PHP program