Calculate a year from a set of dates - php

Question

I am given an array containing periods for a year as following.
$year = '2016';
$periods = [
[
'name' => "Name One",
'startDate' => '01/01/2016',
'endDate' => '03/31/2016'
],
[
'name' => "Name Two",
'startDate' => '04/01/2016',
'endDate' => '12/31/2016'
]
];
The number of periods may vary, hence, the array periods may have any number of elements (say 5 elements, meaning 5 periods for the given year). Now I need to make sure that the periods do really make up a year, that is, two periods cannot overlap and the periods collectively do sum up to be the specified year.
I've tried many different ways, but failed to come up with any efficient solution at all.
I am using Laravel 5, hence Carbon package. But I'll be glad to get this done even in Basic PHP. So all suggestions are welcome

Answer 1

Give this a try - there may be a more elegant solution but I think this works. I've used Carbon, as it's a got some very useful helper methods.
I've assumed your $periods array will be in date order. If it's not, you could just usort it.
$year = '2016';
$periods = [
[
'name' => "Name One",
'startDate' => '01/01/2016',
'endDate' => '03/31/2016'
],
[
'name' => "Name Two",
'startDate' => '04/01/2016',
'endDate' => '12/31/2016'
]
];
// set a start position
$currentPosition = Carbon::create($year, 1, 1)->startOfDay();
// and the end of the year
$endOfYear = Carbon::create($year, 1, 1)->addYear()->startOfDay();
// iterate periods
foreach ($periods as $period) {
$start = Carbon::createFromFormat('m/d/Y', $period['startDate'])->startOfDay();
$end = Carbon::createFromFormat('m/d/Y', $period['endDate'])->endOfDay();
// start of this period should follow the last (??)
if ($start < $currentPosition) {
throw new Exception("$start is earlier than $currentPosition");
}
// must follow on from the current position
if ($currentPosition->diffInDays($start) > 0) {
throw new Exception("$start doesn't follow $currentPosition");
}
// check it doesn't go over the end of the year
if ($currentPosition->addDays($start->diffInDays($end)) > $endOfYear) {
throw new Exception("$end takes us over the end of the year!");
}
$currentPosition = clone $end;
}
// did we reach the end?
if ($currentPosition->addDay()->startOfDay() != $endOfYear) {
throw new Exception("Full year not accounted for");
}
// we're done
echo 'Full year accounted for'.PHP_EOL;