php if statement is not working

$DBRefundExpire value is coming from the MySQL database and is a timestamp(the default timestamp MySQL provides)

the code will echo a message if the timestamp is more than 60 minutes

if(strtotime($DBRefundExpire) > strtotime("-60 minutes")) {
     require('messages/refundExpire.php');
    refundExpiredMsg();
    exit();
} else{
}