PHP date, time related knowledge collection, _PHP tutorial

PHP date and time related knowledge collection,

unix timestamp: the number of seconds elapsed from 0:00 on January 1, 1970 to the current time.

1. Convert date to UNIX timestamp
mktime(): can automatically correct out-of-bounds input

Prototype: mktime(hour, minute, second, month, day, year);
Instance:

<?php
    echo date("Y-m-d",mktime(0,0,0,2,12,2015));   //2015-12-12
    echo date("Y-m-d h:i:s",mktime(7,50,59,10,21,2015)); //2015-10-21 07:50:59
    echo date("Y-m-d",mktime(0,0,0,12,33,2015));   //2016-01-02 ,日期超过31天，自动校正时间
?>

2. Parse the date and time of English text into unix timestamp
strtotime()
Prototype: strtotime(time,now)

<?php
    echo strtotime("now");   //1447987573
    echo date("Y-m-d",strtotime("now"));   //2015-11-20
    echo date("Y-m-d h:i:s",strtotime("now"));   //2015-11-20 02:49:18
    echo date("Y-m-d",strtotime("8 december 2015"));   //2015-12-08
?>

Example: Write an anniversary countdown program through strtotime()

<?php    
        $now = strtotime("now");  //开始时间
	$endTime = strtotime('2018-10-12 10:20:59');  //毕业时间，转成时间戳
	
	$second = $endTime - $now;   //获取从毕业到现在的时间戳（秒数）
	$year = floor($second/3600/24/365);  //从这个时间戳中算出的年数   floor() 函数向下舍入为最接近的整数。
	
	$temp = $second - $year*365*24*3600;  //从时间戳中去掉整年的秒数，就剩下月份的秒数
	$month = floor($temp/3600/24/30);  //换算出月数
	
	$temp = $temp - $month*30*24*3600;  //减去整月的秒数，剩下天数的秒数
	$day = floor($temp/3600/24);  //换算出剩余的天数

	$temp = $temp - $day*24*3600;  //减去整天的秒数，剩下小时的秒数
	$hour = floor($temp/3600);  //换算出剩余的小时数

	$temp = $temp - $hour*3600;  //减去整小时的秒数，剩下分的秒数
	$minute = floor($temp/60);  //换算出剩余的分数

	$second1 = $temp - $minute*60;   //剩余的秒数

	echo "距离毕业还有{$year}年{$month}月{$day}天{$hour}小时{$minute}分{$second1}秒";  //距离毕业还有2年10月27天1小时56分14秒
?>

Extension: Date Calculation
The simplest way to calculate the length between two dates is to calculate the difference between two UNIX timestamps.
Example: Receive the date of birth submitted from the html form in a php script to calculate the age of this user

<?php
        $year = 1989;
	$month = 12;
	$day = 20;
	$birthday = mktime(0,0,0,$month,$day,$year);   //转换成时间戳
	$nowDay = strtotime("now");  //获取到当前日期时间戳
	$ageUnix = $nowDay - $birthday;
	$age = floor($ageUnix/(60*60*24*365));
	echo "年龄:$age";   // 年龄：25
?>

Date and time formatted output
When dates and times need to be saved or calculated, use UNIX timestamp as the standard format.
Disadvantages: unix timestamp format is poorly readable
Solution: call date() to format local time and date
Syntax date(format, timestamp) format a local time and date

<?php    
        date_default_timezone_set('PRC'); //设置中国时区 
	echo date("Y年-m月-d日 H:i:s");   //2015年-11月-20日 17:30:21    
?>

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Instructions: Study Notes

Reference material: "Explanation of PHP"

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