PHP：选择日期范围与日期范围重叠的日期

Question

I would like to know how to get date time ranges overlapping other date time ranges. The particularity is that a date range can have time range overlapping two consecutive days.

For example i have a recurrent reservation the 01/01 and 02/01 beginning at 20:00 and finishing the next day at 02:00.

First day:

$start = '2017-01-01 20:00';
$end =   '2017-01-02 02:00';

Second day:

$start = '2017-01-02 20:00';
$end =   '2017-01-03 02:00';

Now i would like to know how to get reservations overlapping this reservation.

Note: All reservations can have or not time range overlapping day.

For example from a PHP point of view i have the following reservations : Dates and times are represented here as string for readability. In reality they are DateTime.

//The reservation
$reservation= array(
   array(
      'day' => '2017-01-01',
      'time_range' => array('20:00', '23:59')
   ),
   array(
      'day' => '2017-01-02',
      'time_range' => array('00:00', '02:00')
   ),
);

//Other reservations
$reservations= array(
   //Reservation doesn't overlap
   array(
      'day' => '2017-01-01',
      'time_range' => array('18:00', '19:00')
   ),
   //Reservation overlaps
   array(
      'day' => '2017-01-01',
      'time_range' => array('21:00', '22:00')
   ),
   //Reservation overlaps
   array(
      array(
         'day' => '2017-01-01',
         'time_range' => array('23:00', '23:59')
      ),
      array(
         'day' => '2017-01-02',
         'time_range' => array('00:00', '01:00')
     ),
   ),
   ...
);

Thanks!

Answer 1

Use Objects to Make Life Easier

First, you really should simplify your structure. If you really DO have dateTimes everywhere, then reservations should look something more like:

class Reservation
{
    /** @var DateTime $start */
    public $start;
    /** @var DateTime $stop */
    public $stop;

    public function _construct(DateTime $start, DateTime $stop): void
    {
        $this->start = $start;
        $this->stop = $stop;
    }

    public function isOverlapping(Reservation $reservation): bool
    {
        if ($reservation->start >= $this->start && $reservation->start <= $this->stop) {
            // starts during reservation
            return true;
        }

        if ($reservation->stop >= $this->start && $reservation->stop <= $this->stop) {
            // ends during reservation
            return true;
        }

        if ($reservation->start <= $this->start && $reservation->end >= $this->stop) {
            // $this is contained by $reservation
            return true;
        }

        return false;
    }
}

Structuring your reservations this way will allow for some very simple solutions to your problem, like creating RecurringReservation which can generate an array of Reservations for a given date-range. Or a Reservation->isToday() method which could check the $start and $stop properties in cases where it wraps midnight.

For the problem you ask for however:

class Reservation
{

    . . .

    public function anyOverlap(array $reservations): bool
    {
        foreach ($reservations as $checkMe) {
            if ($this->isOverlapping($checkMe)) {
                return true;
            }
        }
        return false;
    }
}

$reservation = new Reservation(new DateTime('2017-01-01 20:00'), new DateTime('2017-01-02 02:00'));

$reservations = [
    new Reservation(new DateTime('2017-01-01 18:00'), new DateTime('2017-01-01 19:00')),
    new Reservation(new DateTime('2017-01-01 21:00'), new DateTime('2017-01-01 22:00')),
    new Reservation(new DateTime('2017-01-01 23:00'), new DateTime('2017-01-02 01:00')),
];

$reservation->anyOverlap($reservations); // true

Edit: I just realised you want an array of overlapping reservations:

class Reservation
{

. . .

public function getOverlapping(array $reservations): array
    {
        $result = [];
        foreach ($reservations as $checkMe) {
            if ($this->isOverlapping($checkMe)) {
                $result[] = $checkMe;
            }
        }
        return $result;
    }
}

. . . 

$overlapping = $reservation->getOverlapping($reservations); // array

One last addendum, use Generators for creating lists of results.

Generators are awesome (when not misused). They offer very high performance when you need a list of results. They're only catch is that you have to pass their result straight into a loop to reap the benefits.

public function getOverlapping(array $reservations): Generator
{
    foreach ($reservations as $checkMe) {
        if ($this->isOverlapping($checkMe)) {
            yield $checkMe;
        }
    }
}

...

foreach($reservation->getOverlapping($reservations) as $overlap) {
    yellAtReceptionistFor($overlap); // ... or whatever 
}

Answer 2

You want to test an appointment start is between the other appointment start and end, then same for the appointment end. If either is true, you have an overlap.