php re-sorting an array - php

Question

I have an array of entries that are separated by year and month like below. I need to sort this array so that entries are "grouped" by year and then by category.
Array
(
[Oct 2011] => Array
(
[0] => Array
(
[title] => CAD Drawing Updates
[file] => /gm-June2010-driver.pdf
[category] => Windows
)
)
[Sep 2011] => Array
(
[0] => Array
(
[title] => title
[file] => /gm-June2010-driver.pdf
[category] => Windows
)
[1] => Array
(
[title] => edges
[file] => /gm-June2010-driver.pdf
[category] =>Walling
)
[2] => Array
(
[title] => Specification update
[file] => /gm-June2010-driver.pdf
[category] => Windows
)
)
)
So this is the sort of thing I'm after.
Array
(
[Oct 2011] => Array
(
[Windows] => Array
(
[0] => Array
(
[title] => CAD Drawing Updates
[file] => /gm-June2010-driver.pdf
)
)
)
[Sep 2011] => Array
(
[Windows] => Array
(
[0] => Array
(
[title] => title
[file] => /gm-June2010-driver.pdf
[category] => Windows
)
[1] => Array
(
[title] => Specification update
[file] => /gm-June2010-driver.pdf
[category] => Windows
)
)
[Walling] => Array
(
[0] => Array
(
[title] => edges
[file] => /gm-June2010-driver.pdf
[category] => Curtain Walling
)
)
)
)
I'm not sure if this is a job for the sort functions, any help would be appreciated, thanks.

Answer 1

No, that can't be done with the sort function, you need to create a new array by iterating through your original array with nested foreach loops.
$newArr = array();
foreach($arr as $month => items) {
foreach($items as $data) {
$newArr[$month][$data["category"]][] = $data;
}
}

Answer 2

You don't want to sort but just to rename keys. PHP Arrays do not support to rename keys directly, so you need to create a new array first that is build with the new keys while maintaining the existing values.
At the end you can replace the original array with the new one:
$rekeyed = array();
foreach($array as $monthYear => &$value)
{
$r = sscanf($monthYear, '%s %d', $month, $year);
if ($r != 2) throw new Exception(sprintf('Invalid Key "%s".', $monthYear));
$categories = array();
foreach($value as &$item)
{
$category =& $item['category'];
unset($item['category']);
$categories[$category][] =& $item;
}
unset($item);
$value =& $categories;
unset($categories);
$rekeyed[$year][$month] =& $value;
}
unset($value);
$array =& $rekeyed;
unset($rekeyed);
print_r($array);
Output:
Array
(
[2011] => Array
(
[Oct] => Array
(
[Windows] => Array
(
[0] => Array
(
[title] => CAD Drawing Updates
[file] => /gm-June2010-driver.pdf
)
)
)
[Sep] => Array
(
[Windows] => Array
(
[0] => Array
(
[title] => title
[file] => /gm-June2010-driver.pdf
)
)
[Walling] => Array
(
[0] => Array
(
[title] => edges
[file] => /gm-June2010-driver.pdf
)
)
)
)
)
Demo

Answer 3

I think the function you should be looking at is uasort.
http://www.php.net/manual/en/function.uasort.php
First do a sort on the main array, the for each element in the array, do a usort on the child array.