Fix TypeError when using $min_booking_date. See GitHub Issue #3773.

web/mrbs_sql.inc

@@ -601,20 +601,19 @@ function mrbsCheckPolicy(array $booking, ?int $ignore_entry_id=null, ?int $ignor
   // Check min_booking_date
   if ($min_booking_date_enabled && !$delete)
   {
-    list($y, $m, $d) = explode('-', $min_booking_date);
-    if (isset($y) && isset($m) && isset($d) && checkdate($m, $d, $y))
+    // Use DateTimeImmutable because we will need the original date for the error message
+    $date_immutable = DateTimeImmutable::createFromFormat($format='Y-m-d', $min_booking_date);
+    // Check that the date is valid (createFromFormat will allow, for example, months > 12)
+    if (($date_immutable === false) || ($date_immutable->format($format) !== $min_booking_date))
     {
-      if ($booking['start_time'] < mktime(0, 0, 0, $m, $d, $y))
-      {
-        $violations[] = get_vocab(
-          'earliest_booking_date',
-          datetime_format($datetime_formats['date'], mktime(0, 0, 0, $m, $d, $y))
-        );
-      }
+      throw new \Exception('MRBS config error: invalid $min_booking_date ' . "'$min_booking_date'");
     }
-    else
+    if ($booking['start_time'] < $date_immutable->setTime(0, 0)->getTimestamp())
     {
-      trigger_error("Invalid min_book_ahead_date", E_USER_NOTICE);
+      $violations[] = get_vocab(
+        'earliest_booking_date',
+        datetime_format($datetime_formats['date'], $date_immutable->getTimestamp())
+      );
     }
   }