How to sort multidimensional arrays in PHP?

Question

If I var_export I get

array (
  0 => 
  array (
    'date' => 2017,
    'id' => 128343,
  ),
  1 => 
  array (
    'date' => 1976,
    'id' => 128315,
  ),
  2 => 
  array (
    'date' => 2006,
    'id' => 128310,
  ),
  3 => 
  array (
    'date' => 1967,
    'id' => 128304,
  ),
  4 => 
  array (
    'date' => 1938,
    'id' => 128295,
  ),
  5 => 
  array (
    'date' => 1978,
    'id' => 128293,
  ),
  6 => 
  array (
    'date' => 1997,
    'id' => 128157,
  ),
  7 => 
  array (
    'date' => 2000,
    'id' => 128124,
  ),

The dates are mixed up. I am trying to sort those dates and keep the Ids attached to each date DESC in order then to loop again but ordered. I tried

function custom_sort_dt($a, $b) {
   return $a['date'] - $b['date'];
}
usort($dateOrdered, "custom_sort_dt");

But I still get wrong order.

// the following gives a date
$myDate = (int)get_post_meta($id, 'usp-custom-14', true);

// this attaches the Id and the date
$dateOrdered[] = array("date"=>$myDate, "id"=>$id);

@Emma updated the question

rob.m
– rob.m

2019-02-07 02:51:22 +00:00
Commented Feb 7, 2019 at 2:51 — rob.m
– rob.m, Commented Feb 7, 2019 at 2:51

Pinke Helga · Accepted Answer · 2019-02-07 03:07:57Z

3

You could use array_multisort.

array_multisort($data, SORT_DESC, array_column($data, 'date'));
var_dump($data);

Note that this function operates on the original array. If you want a copy instead, build one before by

$copy = $data;

edited Feb 7, 2019 at 3:07

answered Feb 7, 2019 at 2:48

Pinke Helga

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1 Comment

Pinke Helga Over a year ago

@Emma See edit, multisort even takes the SORT_DESC constant.

jspcal · Accepted Answer · 2019-02-07 02:41:14Z

0

Perhaps try reversing the comparison to sort in descending order:

return $b['date'] - $a['date'];

answered Feb 7, 2019 at 2:41

jspcal

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3 Comments

rob.m Over a year ago

but look at the var export, the dates are mixed up, so it isn't about reverting the order

jspcal Over a year ago

Interesting rob.m. Can you include the code that sorts and dumps the array?

jspcal Over a year ago

Your question mentions var_export before usort. It doesn't seem you're doing that in the right order.

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