what is the output number of php strtotime(date("Y-m-d h:i:s")) indicates?

Question

I want to find 15 minutes different between link has sent time and link activated time.For that, I am as below,

<?php

$sentTime=strtotime(date("2018-05-29 06:11:42"));
$curTime=strtotime(date("Y-m-d h:i:s"));
$difference=$curTime-$sentTime;

echo $sentTime;
echo '<br>';
echo $curTime;
echo '<br>';
echo $difference;
?>

When I do like this it gives some number, What is those number indicate? If it is time, whether is it in minute or seconds or milli seconds?

Can anybody assist me?

Answer 1

The function strtotime() returns a timestamp, which is the number of seconds elapsed since Jan 01 1970 (UTC).

$sentTime, $curTime and $difference are seconds.

Answer 2

Please use like this way, its the proper way to declare date

  $senttime= date("Y-m-d H:i:s",strtotime("2018-05-29 06:11:42"));