time difference take 2

<!DOCTYPE html>
<html>
<body>

<?php
date_default_timezone_set("America/New_York");

//time from qr code
$qrtime = "11/13/2021 21:26:04";
$parseqrtime = date_create_from_format("m/d/Y H:i:s", $qrtime);
echo "QR time:<br>" . date_format($parseqrtime,"m/d/Y H:i:s"). "<br>";
$qrunix = strtotime(date_format($parseqrtime,"m/d/Y H:i:s"));
echo "QR Unix:<br>" . $qrunix . "<br><br>";

//now time
$signintime = new Datetime("now");
echo "Sign in (now) time:<br>" . date_format($signintime,"m/d/Y H:i:s"). "<br>";
$signinunix = date_format($signintime, 'U');
echo "Sign in Unix:<br>" . $signinunix . "<br><br>";

//get time difference
$timediff = $signinunix - $qrunix;
echo "Unix subtract to get seconds: <br>" . $timediff . "<br/>";


?>

</body>
</html>