使用PHP检测日历事件重叠冲突

I am working on a feature that checks if external events collide with internal events (in a calendar app). The process looks like this:

  • My application creates an array of possible events (called $internalEvents)
  • I source external events from calendars such as Google Calendar, iCloud, etc. (called $externalEvents). These are existing events with the type busy.
  • Now I have to check if there is any kind of conflict regarding internal and external events. I tried something as you can see below but this is by far not correct or bulletproof.

I tried to reduce it to the minimum as much as possible. This is the data input:

$internalEvents = array(
    array(
        "start" => "03/29/2016 12:00:00",
        "end" => "03/29/2016 13:00:00"
    ),
    array(
        "start" => "03/29/2016 12:30:00",
        "end" => "03/29/2016 13:30:00"
    ),
    array(
        "start" => "03/29/2016 13:00:00",
        "end" => "03/29/2016 14:00:00"
    ),
    array(
        "start" => "03/29/2016 13:30:00",
        "end" => "03/29/2016 14:50:00"
    ),
    array(
        "start" => "03/29/2016 14:00:00",
        "end" => "03/29/2016 15:00:00"
    ),
    array(
        "start" => "03/29/2016 14:30:00",
        "end" => "03/29/2016 15:30:00"
    ),
    array(
        "start" => "03/29/2016 15:00:00",
        "end" => "03/29/2016 16:00:00"
    ),
    array(
        "start" => "03/29/2016 15:30:00",
        "end" => "03/29/2016 16:30:00"
    ),
    array(
        "start" => "03/29/2016 16:00:00",
        "end" => "03/29/2016 17:00:00"
    )
);

$externalEvents = array(
    array(
        "start" => "03/29/2016 08:00:00",
        "end" => "03/29/2016 12:00:00",
        "type" => "busy"
    ),
    array(
        "start" => "03/29/2016 15:30:00",
        "end" => "03/29/2016 16:00:00",
        "type" => "busy"
    ),
    array(
        "start" => "03/29/2016 13:30:00",
        "end" => "03/29/2016 14:15:00",
        "type" => "busy"
    )
);

Now I try to find any kind of conflict by comparing the internal event to all external events:

foreach($internalEvents as $internalEvent) {

    $internalEventStart = new DateTime($internalEvent['start']);
    $internalEventEnd = new DateTime($internalEvent['end']);

    $result = true;

    echo "
verifying " . $internalEventStart->format('Y-m-d H:i') . " - " . $internalEventEnd->format('Y-m-d H:i') . "
";

    foreach($externalEvents as $externalEvent) {
        $externalEventStart = new DateTime($externalEvent['start']);
        $externalEventEnd = new DateTime($externalEvent['end']);

        // check if there are conflicts between internal and external events
        if ($internalEventStart >= $externalEventStart && $internalEventStart <= $externalEventEnd) {
            $result = false;
            echo "   problem 1: event is between busy time: " . "
";
        }

        if ($internalEventStart >= $externalEventStart && $internalEventStart <= $externalEventEnd && $externalEventEnd <= $internalEventEnd) {
            $result = false;
            echo "   problem 2: event starts during busy time: " . "
";
        }

        if ($internalEventStart <= $externalEventStart && $externalEventStart <= $internalEventEnd && $internalEventEnd <= $externalEventEnd) {
            $result = false;
            echo "   problem 3: event stops during busy time: " . "
";
        }

        if (($internalEventStart <= $externalEventStart) && ($externalEventStart <= $externalEventEnd) && ($externalEventEnd <= $internalEventEnd)) {
            $result = false;
            echo "   problem 4: event during busy time: " . "
";
        }

        if (($internalEventStart <= $internalEventEnd) && ($internalEventEnd <= $externalEventStart) && ($externalEventStart <= $externalEventEnd)) {
            $result = false;
            echo "   problem 5: event during busy time: " . "
";
        }
    }

    if($result) {
        echo "   result: OK
";
    } else {
        echo "   result: NOT OK 
";
    }
}

I am looking for an algorithm that can find any possible event overlap conflict. Any hint is highly appreciated.

The running code can be found here (IDEone.com).

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douzong6649
douzong6649
2016/03/24 13:03
  • datetime
  • php
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