Convert string to date - Then work out from today how many weeks until the date

dstr.php

// You won't need the string conversion if this is already a date object.

$booking = '18/06/18'; // example string
$date_array = implode('-', array_reverse(explode('/', $booking)));
$now_booking = date('d/m/Y', strtotime($date_array));

$bookDate = DateTime::createFromFormat('d/m/Y', $now_booking);
$waiting = $today->diff($bookDate);
$interval = $waiting->format('%a') / 7;
$weeks = number_format($interval, 1) + 0;