php - how to subtract two dates and times to get difference

Question

i have to sent an email when a user register email contain a link that is become invalid after six hours what i m doing when email is sent i update the db with field emailSentDate of type "datetime" now i got the curent date and time and has made to the same formate as it is in db now i want to find that both these dates and time have differenc of 6 hours or not so that i can make link invalid but i donot know how to do this

my code is look like this i m using hardcoded value for db just for example

$current_date_time=date("Y-m-d h:i:s");
$current=explode(" ",$current_date_time);
$current_date=$current[0];
$current_time=$current[1];
$db_date_time="2010-07-30 13:11:50";
$db=explode(" ",$db_date_time);
$db_date=$db[0];
$db_time=$db[1];

i do not know how to proceed plz help

Answer 1

<?php
//$now = new DateTime(); // current date/time
$now = new DateTime("2010-07-28 01:11:50");
$ref = new DateTime("2010-07-30 05:56:40");
$diff = $now->diff($ref);
printf('%d days, %d hours, %d minutes', $diff->d, $diff->h, $diff->i);

prints 2 days, 4 hours, 44 minutes

see http://docs.php.net/datetime.diff

edit: But you could also shift the problem more to the database side, e.g. by storing the expiration date/time in the table and then do a query like
... WHERE key='7gedufgweufg' AND expires<Now()
Many rdbms have reasonable/good support for date/time arithmetic.