How does PHP get the number of days difference between two dates?

How does PHP get the number of days difference between two dates?  

We often need to get the number of days between two dates to make it easier for customers to know how many days are different from a certain time period, so the results are now becoming more and more popular. No longer shows the date as stiff as it used to be. We've shared here two ways to get the number of days between two dates.

The first type:

01

<?php

02	functioncount_days($a,$b){

03	$a_dt= getdate($a);

04	$b_dt= getdate($b);

"	;    $a _new  =  mktime $a _dt [ ' Mon ' ],  $a _dt [ ' mday ' ],  $a _dt [ ' year ' );

"	;    $b _new  =  mktime $b _dt [ ' Mon ' ],  $b _dt [ ' mday ' ],  $b _dt [ ' year ' );

07	returnround(abs($a_new-$b_new)/86400);

08

}

09

10	//今天与2008年10月11日相差多少天

11	$date1= strtotime(time());

12	$date2= strtotime(‘10/11/2008‘);

13	$result= count_days($date1, $date2);

14	echo$result;

15

?>

The second type:

1

<?php

2	//今天与2008年9月9日相差多少天

3	$Date_1= date("Y-m-d");

4	$Date_2= "2008-10-11";

5	$d1= strtotime($Date_1);

6	$d2= strtotime($Date_2);

7	$Days= round(($d2-$d1)/3600/24);

8	echo"今天与2008年10月11日相差" . $Days. "天";

9

?>

How does PHP get the number of days difference between two dates?