Determining time overlap with PHP

问题

I have a PHP array of "Events", for only 1 day, with start & end times (not entered chronologically) as follows:

$events_list = array(
array(
    'name' => 'Event B',
    'start' => '5:00pm',
    'end' => '6:30pm',
    ),
array(
    'name' => 'Event C',
    'start' => '3:30pm',
    'end' => '5:00pm',
    ),
array(
    'name' => 'Event H',
    'start' => '1:15pm',
    'end' => '2:45pm',
    ),
array(
    'name' => 'Event I',
    'start' => '1:30pm',
    'end' => '4:00pm',
    ),
array(
    'name' => 'Event K',
    'start' => '4:30pm',
    'end' => '5:30pm',
    ),
array(
    'name' => 'Event L',
    'start' => '3:15pm',
    'end' => '5:00pm',
    ),
);

I am trying to visually output these events on a horizontal timeline, something like this:

[* Event H: 1:15pm-2:45pm *]    [* Event L: 3:15pm-5:00pm *][* Event B: 5:00pm-6:30pm *]
    [* Event I: 1:30pm-4:00pm *]        [* Event K: 4:30pm-5:30pm *]
                    [* Event C: 3:30pm-5:00pm *]

(Note that the above are definitely not "drawn to scale".)

As you can see, when an event has an overlapping start/end time, it needs to move to the next line below.

However, I'm having extreme difficulty coming up with a way to accomplish this, especially when an event's start/end times overlap 2 other events (For example, K's start overlaps "Event L", and K's end overlaps "Event B"), causing it to move down 2 lines instead of just 1.

This feels like quite a challenge. Any thoughts or suggestions are very much appreciated!

回答1:

I have already done something like this. Here is a scaled down version of what we do. There is also a simple version of displaying the chart using divs with absolute position.

<?php
$events_list = array(
array(
    'name' => 'Event B',
    'start' => '5:00pm',
    'end' => '6:30pm',
    ),
array(
    'name' => 'Event C',
    'start' => '3:30pm',
    'end' => '5:00pm',
    ),
array(
    'name' => 'Event H',
    'start' => '1:15pm',
    'end' => '2:45pm',
    ),
array(
    'name' => 'Event I',
    'start' => '1:30pm',
    'end' => '4:00pm',
    ),
array(
    'name' => 'Event K',
    'start' => '4:30pm',
    'end' => '5:30pm',
    ),
array(
    'name' => 'Event L',
    'start' => '3:15pm',
    'end' => '5:00pm',
    ),
);
//easier to use timestamps, looping over all rows and overwriting time with timestamp
foreach($events_list as $k=>$v){
    $events_list[$k]['start']=strtotime($v['start']);
    $events_list[$k]['end']=strtotime($v['end']);
}

//sort list by start time. Lowers the number of loops needed below
function cmp($a,$b){
    if($a['start']==$b['start']){
        $aTS = $a['end'];
        $bTS = $b['end'];
    } else {
        $aTS = $a['start'];
        $bTS = $b['start'];
    }
    if($aTS == $bTS)return 0;
    return ($aTS < $bTS)?-1:1;
}
usort($events_list, 'cmp');

//This is where the data will be saved
$levels = array();

//loop over all the events
foreach($events_list as $event){
    //was this event placed in a level already?
    $placed = false;
    //loop through each level checking only the last event
    foreach($levels as $row=>$events){
        //we only need to check the last event if they are already sorted
        $last = end($events);
        //does the current event start after the end time of the last event in this level
        if($event['start'] >= $last['end']){
            //add to this level and break out of the inner loop
            $levels[$row][] = $event;
            $placed = true;
            break;
        }
    }
    //if not placed in another level, add a new level
    if(!$placed){
        $levels[] = array($event);
    }
}

//used for display purposes
$minutesPerPixel = 2;
?>
<html>
<head>
<style type="text/css">
.level {
    background-color:#DDD;
    width:<?=floor(24*60/$minutesPerPixel)?>px;
    border:1px solid #999;
    position:relative;
    height:25px;
}
.event {
    position:absolute;
    overflow:hidden;
    height:19px;
    top:2px;
    background-color:#ACF;
    border:1px solid black;
    padding-left:3px;
    font:9px arial;
    line-height:9px;
}
</style>
</head>
<body>
<?php
//display
foreach($levels as $level){
    echo "<div class='level'>\n";
    foreach($level as $event){
        $left = floor((date('H',$event['start'])*60 + date('i', $event['start']))/$minutesPerPixel);
        $width = floor((($event['end']-$event['start'])/60)/$minutesPerPixel);
        echo "\t<div class='event' style='left:{$left}px;width:{$width}px'>{$event['name']}</div>\n";
    }
    echo "</div>";
}
?>
</body>
</html>

来源：https://stackoverflow.com/questions/17030640/determining-time-overlap-with-php

标签

php

time

timeline

overlap

overlapping