PHP implementation code to calculate the number of days difference between two dates

This article introduces the code implemented in PHP to calculate the number of days between two dates. Friends in need can refer to it.

Calculate the number of days between two dates, code:

<?php 
/**
 * 求两个日期之间相差的天数(针对1970年1月1日之后，求之前可以采用泰勒公式)
 * @param string $day1
 * @param string $day2
 * @return number
 */
function diffBetweenTwoDays ($day1, $day2)
{
    $second1 = strtotime($day1);
    $second2 = strtotime($day2);
     
    if ($second1 < $second2) {
        $tmp = $second2;
        $second2 = $second1;
        $second1 = $tmp;
    }
     
    return ($second1 - $second2) / 86400;
}
 
$day1 = "2013-07-27";
$day2 = "2013-08-04";
 
$diff = diffBetweenTwoDays($day1, $day2);
echo $diff."\n";
?>