PHP（while，date_diff）

Question

I have a past date of appointment set. Every new appointment is 8 days apart from the previous (past appointment+8 days). I would like to create a simple script to return the dates of appointments for the next 365 days starting from the current day each time (i.e. 0=< interval (today-appointment) =< 365).

I've tried something like this but I don't get what I want:

  <?php 
    date_default_timezone_set('Europe/London');

    $today = new DateTime("now");
    $appointment=new DateTime('2013-08-26');
    $interval = $appointment->diff($today)->d; 

    while ($interval <= 365 && $interval => 0)
    {
       echo $appointment->format('l n F Y');
       $appointment->add(new DateInterval('P8D'));
    } ?>

Answer 1

Sum from your question :

1. starting next new appointment is first date from today, that is on +8 day interval from appointment in the past;
2. every next appointment is +8 days from previous one;
3. show appointments only between today and today+365days interval;

date_default_timezone_set('Europe/London');

$today = new DateTime('today');
$appointment = new DateTime('2013-08-23');
$next_appointment_in_days = ceil($appointment->diff($today)->days / 8) * 8;
$next_appointment = clone $appointment;
$next_appointment->modify("+$next_appointment_in_days day");

do {
    echo $next_appointment->format('l, j F Y') . "
";
    $next_appointment->modify('+8 day');
} while ($today->diff($next_appointment)->days <= 365);

Run this code.