PHP days left and gone from date - php

Question

I want to get a user registered date, count the days since registration and show max days left to given days and show message after period ends.
What I got so far works:
$regDatestr = '2020-04-09 19:38:10';
$regDate = strtotime($regDatestr);
$regSince = time() - $regDate;
$days = round ($regSince / ( 60 * 60 * 24 ));
$maxDays = 20;
$maxDaysstr = strtotime("-$maxDays days");
$maxReg = ($regSince + $maxDaysstr);
$daysleft = time() - $maxReg;
$restDays = round ($daysleft / ( 60 * 60 * 24 ));
if ($regdate <= $maxDaysstr) :
echo 'period ended'
else :
echo 'Registered since' . $days . ' .days . Rest days ' . $restDays . '
endif;
$daysleft and days gives me the right days. But the period doesnt end exact after 20 days.
What I need is max 20 days since registration date. So when
'2020-04-09 19:38:10';
plus 20 days should end the period at
'2020-04-29 19:38:10';
but it seems my if condition doesnt work as expected. So Im getting "Registered since 21 days. Rest days 0".
Why is that so?

Answer 1

Because you have an typo in with your variable names
if ($regdate <= $maxDaysstr)
should be
if ($regDate <= $maxDaysstr)
and your code could be shorter
$regDatestr = '2020-04-01 19:38:10';
$regDate = new DateTime($regDatestr);
$diffToday = $regDate->diff(new DateTime());
$maxDays = 10;
$diffMax = $regDate->diff(new DateTime("-$maxDays days"));
if ($diffMax->invert == 0) :
echo 'period ended';
else :
echo 'Registered since ' . $diffToday->days . ' .days . Rest days ' . $diffMax->days;
endif;