Sort Multidimensional Array in PHP based on date [duplicate] - php

Question

This question already has answers here:
How can I sort arrays and data in PHP?
(14 answers)
Closed 8 years ago.
I have an array that looks something like this:
Array
(
[0] => Array
(
[id] => 4
[date] => 15.12.2014
[archived] => 0
)
[1] => Array
(
[id] => 3
[date] => 19.12.2014
[archived] => 0
)
[2] => Array
(
[id] => 6
[date] => 15.11.2014
[archived] => 0
)
)
What I would like to do is sort the items into high-to-low order in the first dimension based on the date value in the second dimension. I can use strtotime() on the [date] field and produce a unix timestamp (please note, these dates are in Australian format and not US. The server produces the correct timestamp).
I'm aware that I can use arsort() to arrange this array, but I'm not sure how to do it based on the value of a second dimension array key.
I need the array to look like this:
Array
(
[0] => Array
(
[id] => 3
[date] => 19.12.2014
[archived] => 0
)
[1] => Array
(
[id] => 4
[date] => 15.12.2014
[archived] => 0
)
[2] => Array
(
[id] => 6
[date] => 15.11.2014
[archived] => 0
)
)
How can I best achieve this in PHP?
I've tried various arrangements of the following to no avail:
arsort($items, strtotime(['date']))

Answer 1

You should use usort
In your case:
usort($items, function($a, $b) {
return strtotime($a['date']) - strtotime($b['date']);
});

Answer 2

Suppose that your $array is declared that way:
$my_array = array(
array(
'id'=>4,
'date'=>'19.12.2014',
'archived'=>0),
array(
'id'=>3,
'date'=>'15.12.2014',
'archived'=>0),
array(
'id'=>6,
'date'=>'15.11.2014',
'archived'=>0));
You can use usort function with a closure function as follows
usort($my_array, function($a, $b) {
return strtotime($a['date']) - strtotime($b['date']);
});
usort will sort your array "in place", means that no copy of array will be returned but original array is sorted.
Moreover, I've used strtotime to make order between dates as a starting dates are represent as strings and not in "real date" format.
Moreover keep in mind that
Note: This function assigns new keys to the elements in array. It will remove any existing keys that may have been assigned, rather than
just reordering the keys.
Execution test
Array
(
[0] => Array
(
[id] => 6
[date] => 15.11.2014
[archived] => 0
)
[1] => Array
(
[id] => 4
[date] => 15.12.2014
[archived] => 0
)
[2] => Array
(
[id] => 3
[date] => 19.12.2014
[archived] => 0
)
)