PHP check if variable is smaller than previous item in array - php

Question

I need a way to check if there are events that overlap each other. So I made an array with the start and end hour of every event. It looks like this:
Array
(
[0] => Array
(
[start] => 0930
[end] => 1200
)
[1] => Array
(
[start] => 1000
[end] => 1230
)
[2] => Array
(
[start] => 1300
[end] => 1530
)
)
This is what I've tried to check if there are events that overlap:
if ( $orders->have_posts() ):
while ($orders->have_posts()) : $orders->the_post();
foreach($order as $o){
$start = $o['start'];
$end = $o['end'];
$attractieID = $o['attractie']->ID;
foreach($order as $key => $attractieID){
$slots[] = array('start' => $start, 'end' => $end);
if($start < $end){
//overlap
}else{
//no overlap
}
}
}
endwhile;
endif;
But this will always give true since I am checking the start and end date of the same item in my array.
I need to way to compare the start value of the current array item and the end value of the previous array item
Anyone knows if this is even possible?
Many thanks in advance!

Answer 1

Start looping at index 1, and compare the start time of the current event with the end of the event with index-1.
$count = count($order);
for ($i = 1; $i < $count; $i++) {
if ($order[$i]['start'] < $order[$i-1]['end']) {
// overlap
} else {
// no overlap
}
}
If you want to do this while also copying from $order to slots, you can use a variable to hold the end time from the previous iteration.
$prevEnd = null;
foreach($order as $o){
$start = $o['start'];
$end = $o['end'];
$attractieID = $o['attractie']->ID;
$slots[] = array('start' => $start, 'end' => $end);
if($prevEnd !== null && $start < $prevEnd){
//overlap
}else{
//no overlap
}
$prevEnd = $end;
}
DEMO

Answer 2

Try this code, with a for loop instead of foreach:
for($i=0;$i<count($order);i++){
$slots[] = array('start' => $start, 'end' => $end);
if($order[$i+1]){
if($order[$i]['start'] < $order[$i+1]['end']{
//overklap
}else{
//no overlap
}
}

Answer 3

Just use a normal for loop. And, to be sure everything is right, sort the array before checking it (if you are sure it is gona be sorted, you can skip that part)
$sortedOrders = usort($order, function($a, $b)
{
$aStart = $a['start'];
$bStart = $b['start'];
return ($a < $b) ? -1 : 1;
});
$count = count($sortedOrders);
for($i = 1; $i < $count; $i++)
{
if($sortedOrders[$i - 1]['end'] > $sortedOrders[$i]['start'])
{
// Handle overlap
}
}