PHP series on the use of date functions

  • 2020-05-19 04:28:12
  • OfStack

PHP is a very amazing language. It's powerful enough (the core language of the biggest blog (wordpress)), it's broad enough (it runs on the biggest social network, facebook), and it's simple enough (it's the language of choice for beginners). It works well on low cost machines. Also, the php language has some great server suites (WAMP and MAMP) that are easy to install on your machine. PHP has a very rich library that makes it easy for developers to do business. Since we work with dates the most in our projects, we'll start with date functions today.
Take a simple example of date
I'll output the content to our client (browser) using the echo command. I'll use the following code as the base code.
<!DOCTYPE html> 
<html lang="en"> 
<meta charset="utf-8" /> 
<title>Getting started with dates in php5</title> 
echo "Today is ",date('l'); 

You will see the following in your browser.
Today is Friday 

This function outputs the text format of the day of the week. The date function requires at least one character parameter (this parameter tells us how to format the current date).
Try different formats
If you read PHP date function in the php manual, you will find that there are many ways to format a date.
<?php echo "Today is ",date('Y-m-d'); ?> 

Will get
Today is 2012-08-17
There are some dates that are commonly used, so PHP provides some constants for you to use. For example, you can use Cookie to get the client date.
<?php echo "Today is ",date(DATE_COOKIE); ?> 

You will get the following
Today is Friday, 17-Aug-12 11:34:38 CST 

Be careful not to use quotation marks when using constants.
What time is it now?
If you want to output the current time, you can use date.
<?php echo "The time is ",date('g:i:sa'); ?> 

You will get
The time is 11:39:59am
Localize your time zone
If you find that the code above doesn't give you the correct time, it's probably because your server has a different time zone than your own. You need to specify a time zone on the server, so you use the following code:
<?php date_default_timezone_set('Asia/Shanghai'); ?> 

This will set the time zone of Shanghai, China. This is a function of php5 (note the older version of php) and there are many time zones you can choose. If you want to make it permanent, you can modify your php.ini file.
Get other times
You often need other time than the present time. When you create a time using the date() function, the system will use Unix system time. This time represents the number of seconds from 00:00:00 on January 1, 1970, GMT (Unix era time) to the present time.
To specify how to get the date of the specified time, you can provide the number of seconds as the second parameter of the date(0 function.
<?php echo "Today is ",date('Y-m-d', 1309133434); ?> 

The result is:
Today is 2011-06-27
This doesn't seem to be useful, but it means you can do the calculation using the date() function. To do this, you need to simply create a timestamp.
Create timestamp
There are many ways to create a timestamp. We can use the mktime() function to get the timestamp we need.
$mytime=mktime(9, 23, 33, 6, 26, 2011); 
echo "Today is ",date('Y-m-d g:i:sa', $mytime); 

The result is:
Today is 2011-06-26 9:23:33am
The mktime() function requires you to pass in hours, minutes, seconds, months, days, and years. This is a good way to get a timestamp, but there are cooler ways.
Get the timestamp by the character
You can get the timestamp using the strtotime() function, which converts readable characters to Unix timestamps. The PHP is quite flexible in converting characters into timestamps, so you can insert various values to get the timestamp you want.
Here's a simple example:
$mytime=strtotime("7:50pm June 26 2011"); 
echo "Today is ",date('Y-m-d g:i:sa', $mytime); 

Today is 2011-06-26 7:50:00pm
PHP is quite clever at interpreting characters, but not perfect, so always test the characters you enter before you insert them. Using "english-like instructions" to convert to the required timestamp is a very good way to do this. You can do this like the following:
$nextfriday=strtotime("next Friday"); // Next week, 5 
$nextmonth=strtotime("+1 Month"); // Count from today 1 Months from now  
$lastchristmas=strtotime("-1 year dec 25"); // Last Christmas  

Get date range
The values that strtotime returns are converted to Numbers, and we can do basic operations with those Numbers, and we can do a lot of really interesting things with those Numbers. For example, if you need to teach a subject twice a week for 16 weeks, you want to get the time you need to teach the subject. You can do the following.
$startdate = strtotime('next Tuesday'); 
$enddate = strtotime('+16 weeks', $startdate); 
$currentdate = $startdate; 
echo '<ol>'; 
while($currentdate < $enddate): 
echo "\t<li>", date('M d', $currentdate); 
$currentdate = strtotime('+1 week', $currentdate); 
echo '</ol>'; 

You will get the following results:
Aug 21 
Aug 28 
Sep 04 
Sep 11 
Sep 18 
Sep 25 
Oct 02 
Oct 09 
Oct 16 
Oct 23 
Oct 30 
Nov 06 
Nov 13 
Nov 20 
Nov 27 
Dec 04 

Note 1 next line: $currentdate = strtotime("+1 week", $currentdate). In this line, you will find that you need to specify 1 timestamp as the second parameter. strtotime will use this parameter instead of the default timestamp (today) and perform the operation.
The number of days to a certain date
When we use a calculator, we try to calculate the number of days to a given day. You can easily calculate the time stamp for the 4th week of November.
$someday = strtotime("3 weeks thursday November 1"); 
$daysUtilDate = ceil(($someday - time())/60/60/24); 
echo "There are ", $daysUtilDate, " until Thanksgiving"; 

First, we start to calculate the date of Thanksgiving (week 4 after November 1), and then we calculate the number of days between Thanksgiving and the present time through simple arithmetic. When we compare, we can use time(), because it returns the number of epoch seconds to the current time.
Have a special liking
If you start learning php, learning dates is the best way to learn the language, because dates have a lot of interesting things to do with them. Explore the date and time related functions in the manual. Please share what you have learned.

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