Find discontinuities in an array of date in php - php

Question

I have a sorted array of dates that looks like so :
$dates = Array('2014-10-01','2014-10-01','2014-10-02','2014-10-03','2014-10-05');
In this array we have two times (sometimes more, but it's normal in my script) the date Oct 1st but it's missing the 4th.
How can I detect that there is a discontinuity between the first value of the array, and the last value of the array (again, my array is sorted by ascending dates) ?

Answer 1

$dates = array('2014-10-01','2014-10-01','2014-10-02','2014-10-03','2014-10-05');
$continued = true;
foreach ($dates as $key => $date) {
if (!empty($dates[$key+1])) {
$cDate = new DateTime($date);
$next = new DateTime($dates[$key+1]);
$interval = $next->diff($cDate);
if ($interval->d > 1) {
$continued = false;
}
}
}
$continued = false then discontinuity present.

Answer 2

It's probably worth looking into the DateTime class, and its goodies. In particular DateTime::diff, which returns a DateInterval instance. This enables you to safely subtract 2 dates, and determine what the time difference between those dates actually is. cf the manual.
In short, I've put together a little function that can be used to determine oddities in an array of date strings:
$dates = array('2014-10-01','2014-10-01','2014-10-02','2014-10-03','2014-10-05');
$obj = array();
foreach ($dates as $date)
{//create an array of DateTime instances from the $dates values
$obj[] = new DateTime($date);
}
/**
* #param array $dates (an array of DateTime instances)
* #param string $intervalProperty = 'd' (valid valus are y, m, d, h, i, s)
* #param int $interval = null (the value $intervalProperty should have)
* #return array of null|DateInterval
*/
function getOddDiffs(array $dates, $intervalProperty = 'd', $interval = null)
{
$diffs = array();
for($i=0, $j=count($dates)-1;$i<$j;++$i)
{//iterate $dates
$diff = $dates[$i]->diff($dates[$i+1]);//compute diff
if ($interval === null && $diff->{$intervalProperty})
$interval = $diff->{$intervalProperty};//set $interval if needed/possible
if ($diff->{$intervalProperty} !== $interval)
{//if interval value !== $interval (type+value check required in case $interval is null)
$diffs[] = $diff;//return the diff
}
else
{
$diffs[] = null;//null means ok
}
}
return $diffs;//return results
}
If you want to see it in action:
Demo here

Answer 3

function hasDiscontinuities($dates)
{
// remove duplicates
$dates = array_unique($dates);
// get the last day
$parts = explode('-', end($dates));
$lastDay = (int) $parts[2];
// if the amount of dates is smaller than the last day, there must be discontinuities
if (count($dates) < $lastDay) {
return true;
}
return false;
}
Edit regarding Elias Van Ootegem's comment, duplicates now are threated as discontinuities:
function hasDiscontinuities($dates)
{
// duplicates count as discontinuities
if ($dates != array_unique($dates)) {
return true;
}
// get the last day
$parts = explode('-', end($dates));
$lastDay = (int) $parts[2];
// if the amount of dates is smaller than the last day, there must be discontinuities
if (count($dates) < $lastDay) {
return true;
}
return false;
}
Second edit because of the added details in the comments:
function hasDiscontinuities($dates)
{
// duplicates count as discontinuities
if ($dates != array_unique($dates)) {
return true;
}
$firstDate = new DateTime($dates[0]);
$lastDate = new DateTime(end($dates));
// if the difference in days is not the same as the amount of elements in the array, there are discontinuities
if (count($dates) != $lastDate->diff($firstDate)->days + 1) {
return true;
}
return false;
}