Sort Multi Array in PHP

Question

Does anybody have an idea how can I sort this array by key (date) in PHP?

Array
(   
    [2011-02-16] => Array
        (
            [date] => 2011-02-16
          


        

Answer 1

http://www.php.net/manual/en/function.array-multisort.php

Would example #3 suit your needs?

Answer 2

A better answer would be to use uksort which is used to sort keys with a user-defined function (considering that these dates cannot always be compared and cannot be sorted with ksort without first applying strtotime to the keys):

function sort_by_date_keys($date_key1, $date_key2) {
    // reverse the order of the $date_keys for "oldest to newest"
    return strtotime($date_key2) - strtotime($date_key1);
);

uksort($array, 'sort_by_date_keys');

This method is more defined than uasort as it was tailored for keys.

Example:

$array = array(
    '1/1/12' => 'foo1',
    '1/1/13' => 'foo2'
);
uksort($array, 'sort_by_date_keys');

// output
$array = array(
    '1/1/13' => 'foo2',
    '1/1/12' => 'foo1'
);

Answer 3

Since your array already has the date in the keys, why not just use ksort? The string comparison should work fine since you're using YYYY-MM-dd format.