string & int not working properly in strtotime - php

Question

In this case $interval i am giving as integer means it is working fine returning true, suppose $interval i am giving as string means not working properly returning false.
scenario 1
<?php
$restDate = "2018-11-21 11:58:55";
$difference = strtotime(date('Y-m-d H:i:s')) - strtotime($restDate);
$interval = 60 * 60 * 24 * 7;
if($difference <= $interval){
$data['passwordResetStatus'] = true;
}else{
$data['passwordResetStatus'] = false;
}
var_dump($data);
?>
Output
array(1) { ["passwordResetStatus"]=> bool(true) }
scenario 2
<?php
$restDate = "2018-11-21 11:58:55";
$difference = strtotime(date('Y-m-d H:i:s')) - strtotime($restDate);
$interval = "60 * 60 * 24 * 7"; // changes from here
if($difference <= $interval){
$data['passwordResetStatus'] = true;
}else{
$data['passwordResetStatus'] = false;
}
var_dump($data);
?>
Output
array(1) { ["passwordResetStatus"]=> bool(false) }
My expected out
scenario 2 also it should return as array(1) { ["passwordResetStatus"]=> bool(true) }

Answer 1

Instead of having the user input "60*60*24*7", can't the user input "1 week"?
If yes a much safer way than eval is to use strtotime to compute the time.
echo strtotime("1 week")-time();
// Same as 60*60*24*7

Answer 2

Obviously you cannot put math equations in string, but if for some reason you got them in string format, and you are sure they will be always is format like this, you can parse it..
f.e.:
$interval = array_product(explode('*',"60 * 60 * 24 * 7"));

Answer 3

Why not working with the PHP DateTime classes? Here 's a short solution.
$today = new \DateTime();
$rest = new \DateTime('2018-11-21 11:58:55');
$interval = $rest->diff($today);
$passwordValid = $interval->format('%a') >= 7 ? false : true;
What I 've done here? First we need todays time. After that we need the time, with which we compare todays time. Both times are DateTime instances. Because of that we can calculate the difference between both time pretty easy. The DateTime class got the diff method, which calculates the difference between two DateTime objects. It returns a DateInterval object, which holds the difference. Now we can compare the calculated difference with your interval of 7 days.
Pretty easy, hm?