How to Group PHP Array Based On Year with Nested Array - php

Question

My Current PHP Array Outputs like this:
Array
(
[0] => Array
(
[year] => 2015
[month] => November
)
[1] => Array
(
[year] => 2015
[month] => October
)
[2] => Array
(
[year] => 2015
[month] => September
)
[3] => Array
(
[year] => 2015
[month] => August
)
[4] => Array
(
[year] => 2015
[month] => July
)
[5] => Array
(
[year] => 2015
[month] => June
)
[6] => Array
(
[year] => 2015
[month] => May
)
[7] => Array
(
[year] => 2015
[month] => April
)
[8] => Array
(
[year] => 2015
[month] => March
)
[9] => Array
(
[year] => 2015
[month] => February
)
[10] => Array
(
[year] => 2015
[month] => January
)
[11] => Array
(
[year] => 2014
[month] => December
)
[12] => Array
(
[year] => 2014
[month] => November
)
[13] => Array
(
[year] => 2014
[month] => October
)
[14] => Array
(
[year] => 2014
[month] => September
)
[15] => Array
(
[year] => 2014
[month] => August
)
[16] => Array
(
[year] => 2014
[month] => July
)
)
I want to sort the above Array and group them based on the Year. The Array I want to convert the above is to get like this:
Array (
[0] => Array
(
[yearGroup] => “2015”
[dates] => Array
(
[0] => Array
(
[year] => 2015
[month] => November
)
[1] => Array
(
[year] => 2015
[month] => October
)
…etc..etc…
)
)
[1] => Array
(
[yearGroup] => 2014
[dates] => Array
(
[0] => Array
(
[year] => 2014
[month] => December
)
[1] => Array
(
[year] => 2014
[month] => November
)
…etc..etc…
)
)
)
This is the code I have tried so far:
$calendar = // ..... The Array Above .....;
$sidebarCalendar = array();
$currentYear = '';
$i = 0;
foreach ($calendar as $date) {
if ($currentYear != $date['year']) {
$currentYear = $date['year'];
$i++;
$tempYearDates = array();
$j = 0;
$tempYearDates[$j] = array(
'year' => $date['year'],
'month' => $date['month']
);
$j++;
// Add to Array
$sidebarCalendar[$i] = array (
'yearGroup' => $date['year'],
'dates' => $tempYearDates
);
}
else {
$tempYearDates = array(
'year' => $date['year'],
'month' => $date['month']
);
// Locate the Array Tree
$currentParent = $sidebarCalendar[$i];
$currentArray = $currentParent['dates'];
$currentArray[$j] = $tempYearDates;
$j++;
}
}
But the above outputs incomplete array like this:
Array
(
[1] => Array
(
[yearGroup] => 2015
[dates] => Array
(
[0] => Array
(
[year] => 2015
[month] => November
)
)
)
[2] => Array
(
[yearGroup] => 2014
[dates] => Array
(
[0] => Array
(
[year] => 2014
[month] => December
)
)
)
)
Can someone point out what I have got wrong here please? If there is a better way to do the same instead of the above method, please do guide me there please…

Answer 1

You could use some of the builtin PHP's array functions to solve this issue. First thing you want to do is get all the unique years in that array, so you could do:
$years = array_unique(array_map(function($item) { return $item['year']; }, $calendar));
Here, I've used array_map to get an array containing only the year property for each item, and fed it to the array_unique function to get only unique values.
Next thing you could do is iterate through all the years, and populate another array, something like this:
$grouped = [];
foreach($years as $year) {
$grouped[$year] = array_filter($calendar, function($item) use ($year) { return $item['year'] === $year; });
}
This way you'll get a key for each year in the grouped variable, and each key will contain a subarray composed only of the elements of calendar satisfying the array_filter condition.
I'm sure there are better / more optimized ways of doing this (maybe using array_walk or array_reduce?) and I encourage you to find those! Still, remember that there are many array functions builtin in PHP, read their documentation and learn when to use them, they'll be of great help!
Edit: I realize that the output of my solution is not exactly what you're expecting, but it's very easily adaptable. I myself prefer using keyed arrays (maps?) whenever possible in place of regular arrays with properties, but to each their own!
$grouped = [];
foreach($years as $year) {
$grouped[] = [
'yearGroup' => $year,
'dates' => array_filter($calendar, function($item) use ($year) { return $item['year'] === $year; })
];
}
Edit 2: Sometimes I forget how to PHP.