Calculate intersection between 2 date ranges - php

Question

i would like to calculate the number of free days (absences) in a specific week. I use an API that returns the following data:
{
"count": 1,
"data": [
{
"id": "11ec62ff1df2654d8bd6f1d234a6c496",
"type": "HOLIDAY",
"from": "2021-12-22",
"to": "2021-12-23",
"resourceId": "11ec46d6547a00728be3e1ed8ff29535",
"createdAt": "2021-12-22T08:14:00"
}
],
"success": true
}
These are vacation and sickness data. I have a weekly report where I need to calculate the number of absence days during that week. I need to find an easy way to calculate the number of absence days during the week.
I have tried by using https://www.php.net/manual/de/datetime.format.php and convert it into "z" format, but it doesn't look elegant and from performance perspective i think it's not best.
//The week range
$weekStart = new DateTime("2021-12-20");
$weekEnd = new DateTime("2021-12-24");
//The Planned absence
$absenceStart = new DateTime("2021-12-22");
$absenceEnd = new DateTime("2021-12-23");
//Specify the DateInterval for calculating the period
$interval = DateInterval::createFromDateString('1 day');
//Need to add the interval to the end date in order to consider the end as well
$weekEnd->add($interval);
$absenceEnd->add($interval);
//Getting the 2 periods week and absence
$weekPeriod = new DatePeriod($weekStart, $interval, $weekEnd);
$absencePeriod = new DatePeriod($absenceStart, $interval, $absenceEnd);
$weekArray = array();
$absenceArray = array();
//put the day number format('z') into an array of the week
foreach ($weekPeriod as $i => $dt) {
$weekArray[$i] = $dt->format('z');
}
//put the day number format('z') into an array of the absence
foreach ($absencePeriod as $i => $dt) {
$absenceArray[$i] = $dt->format('z');
}
//get the intersection between both arrays
$ergebnis = array_intersect($weekArray, $absenceArray);
//calculate the number of entries
echo "The employee has <b>".count($ergebnis)."</b> free days in the week from 2021-12-20 until 2021-12-24";
This is returning the right information.
The employee has 2 free days in the week from 2021-12-20 until 2021-12-24
Can anyone please suggest if there is a better way or if i can tweak at least to make it more elegant and performat?
Thanks alot

Answer 1

Instead of looping over the week array, absence array, then week array again (array_intersect), you could eliminate looping through the absence array and the second week array loop if that information is not needed. So you only have 1 loop instead of 3 should be more performant.
//The week range
$weekStart = new DateTime("2021-12-20 00:00:00");
$weekEnd = new DateTime("2021-12-24 23:59:59");
//The Planned absence
$absenceStart = new DateTime("2021-12-22 00:00:00");
$absenceEnd = new DateTime("2021-12-23 23:59:59");
//Specify the DateInterval for calculating the period
$interval = DateInterval::createFromDateString('1 day');
//Getting the available period
$weekPeriod = new DatePeriod($weekStart, $interval, $weekEnd);
$availableDayCount = 0;
//put the day number format('z') into an array of the week
foreach ($weekPeriod as $dt) {
// Filter out days the employee is absent.
if($dt < $absenceStart || $dt > $absenceEnd) {
$availableDayCount += 1;
}
}
//calculate the number of entries
echo "The employee has <b>" . $availableDayCount . "</b> free days in the week from " . $weekStart->format('Y-m-d') . " until " . $weekEnd->format('Y-m-d');
Additionally, it didn't appear to be providing the correct information (maybe I am wrong?). Your question states it came to 2 days but I count 3:
2021-12-20
2021-12-21
2021-12-24
(The 22nd and 23rd being absent)
If that is incorrect, you can change $weekEnd to 2021-12-23 (I added start/end of day times so the entire day is counted).