Use the diff() method of PHP’s DateTime class like this:-
$lastWeek = new DateTime('last thursday');
$now = new DateTime();
var_dump($now->diff($lastWeek, true));
This will give you a DateInterval object:-
object(DateInterval)[48]
public 'y' => int 0
public 'm' => int 0
public 'd' => int 2
public 'h' => int 11
public 'i' => int 34
public 's' => int 41
public 'invert' => int 0
public 'days' => int 2
Retrieving the values you want from that is trivial.