sorting an array which its values are associate array

Question

I have an array that its values are associate arrays. I need sort this array based on keys;

$list = array (
    array("post_id"=>"2","date"=>"2015","title"=>"title2"),
    array("post_id"=>"4","date"=>"2017","title"=>"title4"),
    array("post_id"=>"3","date"=>"2016","title"=>"title3"),
    array("post_id"=>"1","date"=>"2014","title"=>"title1")
);

For example sorting this array by post_id which means turn that array to this:

$list = array (
    array("post_id"=>"1","date"=>"2014","title"=>"title1"),
    array("post_id"=>"2","date"=>"2015","title"=>"title2"),
    array("post_id"=>"3","date"=>"2016","title"=>"title3"),
    array("post_id"=>"4","date"=>"2017","title"=>"title4")


);

I searched this forum and find this code:

function array_sort($array, $on, $order=SORT_ASC){

$new_array = array();
$sortable_array = array();

if (count($array) > 0) {
    foreach ($array as $k => $v) {
        if (is_array($v)) {
            foreach ($v as $k2 => $v2) {
                if ($k2 == $on) {
                    $sortable_array[$k] = $v2;
                }
            }
        } else {
            $sortable_array[$k] = $v;
        }
    }

    switch ($order) {
        case SORT_ASC:
            asort($sortable_array);
            break;
        case SORT_DESC:
            arsort($sortable_array);
            break;
    }

    foreach ($sortable_array as $k => $v) {
        $new_array[$k] = $array[$k];
    }
}

return $new_array;}

but I cant understand what is it exactly doing. the topic link is: Sort PHP multi-dimensional array based on key?

http://php.net/manual/en/function.usort.php perhaps? – GordonM Jan 30 '17 at 14:40 — GordonM, Jan 30 '17 at 14:40

Tom · Accepted Answer · 2017-01-30T14:35:45.600

You're not sorting by key, so the example you found won't work for you. A simple usort will do it;

$list = array (
    array("post_id"=>"2","date"=>"2015","title"=>"title2"),
    array("post_id"=>"4","date"=>"2017","title"=>"title4"),
    array("post_id"=>"3","date"=>"2016","title"=>"title3"),
    array("post_id"=>"1","date"=>"2014","title"=>"title1")
);

function sortPosts($a, $b)
{
    if ($a['post_id'] == $b['post_id']) {
        return 0;
    }
    return ($a['post_id'] < $b['post_id']) ? -1 : 1;
}


usort($list, "sortPosts");

This passes your $lists array into a function and compares each of its values - you can see we're comparing the ['post_id'] value for each.

As the post_id's are strings in your original array, you may need to typecast these as integers, but see how you go.

yeap thank you.i use it and its work.the code in that link is working too.thanks a lot — Alireza Seyedzade, Jan 30 '17 at 14:34

arkascha · Answer 2 · 2017-01-30T13:53:18.957

Most elegant usually is to use the usort() function combined with a closure.

Take a look at this simple demonstration:

<?php

$list = [
    ["post_id"=>"2","date"=>"2015","title"=>"title2"],
    ["post_id"=>"4","date"=>"2017","title"=>"title4"],
    ["post_id"=>"3","date"=>"2016","title"=>"title3"],
    ["post_id"=>"1","date"=>"2014","title"=>"title1"]
];

usort(
  $list,
  function($a, $b) {
    return $a['post_id'] < $b['post_id'];
  }
);
print_r($list); // First output, descending order

usort(
  $list,
  function($a, $b) {
    return $a['post_id'] > $b['post_id'];
  }
);
print_r($list); // Second output, ascending order

Note the reversed comparison operator in the two calls, < versus >...

The output of that obviously is:

First output, descending order:

Array
(
    [0] => Array
        (
            [post_id] => 4
            [date] => 2017
            [title] => title4
        )

    [1] => Array
        (
            [post_id] => 3
            [date] => 2016
            [title] => title3
        )

    [2] => Array
        (
            [post_id] => 2
            [date] => 2015
            [title] => title2
        )

    [3] => Array
        (
            [post_id] => 1
            [date] => 2014
            [title] => title1
        )

)

Second output, ascending order:

Array
(
    [0] => Array
        (
            [post_id] => 1
            [date] => 2014
            [title] => title1
        )

    [1] => Array
        (
            [post_id] => 2
            [date] => 2015
            [title] => title2
        )

    [2] => Array
        (
            [post_id] => 3
            [date] => 2016
            [title] => title3
        )

    [3] => Array
        (
            [post_id] => 4
            [date] => 2017
            [title] => title4
        )

)

score 1 · Answer 3 · answered Jan 30 '17 at 13:49

I use this function :

function aasort (&$array, $key) {
    $sorter=array();
    $ret=array();
    reset($array);
    foreach ($array as $ii => $va) {
        $sorter[$ii]=$va[$key];
    }
    asort($sorter);
    foreach ($sorter as $ii => $va) {
        $ret[$ii]=$array[$ii];
    }
    $array=$ret;
    return $array;
}

$list = array (
    array("post_id"=>"2","date"=>"2015","title"=>"title2"),
    array("post_id"=>"4","date"=>"2017","title"=>"title4"),
    array("post_id"=>"3","date"=>"2016","title"=>"title3"),
    array("post_id"=>"1","date"=>"2014","title"=>"title1")
);

$outputArray = aasort($list,"post_id");

score 1 · Answer 4 · answered Jan 30 '17 at 13:58

1

That probably wasn't the best answer to chose from that question. Just extract the column to sort on, and sort that to sort the original:

array_multisort(array_column($list, 'post_id'), SORT_ASC, $list);

answered Jan 30 '17 at 13:58

AbraCadaver

78,200
7
66
87

score 1 · Answer 5 · answered Jan 30 '17 at 14:00

You can use following code:

<?php
$list = array (
    array("post_id"=>"2","date"=>"2015","title"=>"title2"),
    array("post_id"=>"4","date"=>"2017","title"=>"title4"),
    array("post_id"=>"3","date"=>"2016","title"=>"title3"),
    array("post_id"=>"1","date"=>"2014","title"=>"title1")
);

$sorted = array_orderby($list, 'post_id', SORT_ASC);

echo "<pre>";
print_r($sorted);

function array_orderby()
{
    $args = func_get_args();
    $data = array_shift($args);
    foreach ($args as $n => $field) {
        if (is_string($field)) {
            $tmp = array();
            foreach ($data as $key => $row)
                $tmp[$key] = $row[$field];
            $args[$n] = $tmp;
            }
    }
    $args[] = &$data;
    call_user_func_array('array_multisort', $args);
    return array_pop($args);
}
?>

It will produce following output:

Array
(
    [0] => Array
        (
            [post_id] => 1
            [date] => 2014
            [title] => title1
        )

    [1] => Array
        (
            [post_id] => 2
            [date] => 2015
            [title] => title2
        )

    [2] => Array
        (
            [post_id] => 3
            [date] => 2016
            [title] => title3
        )

    [3] => Array
        (
            [post_id] => 4
            [date] => 2017
            [title] => title4
        )

)

JustOnUnderMillions · Answer 6 · 2017-01-30T14:21:52.793

The function in OP question does:

first collects all values via $on from the subarray (first foreach) and binds it to the $sortable_array via original_array key $k. Like $list[0]['post_id']; is collect in: $sortable_array[0];
After all values are collected, the array will be sorted DESC or ASC (see switch) with asort, that keeps the index=>value connection. So $sortable_array looks like: Before [0=>2,1=>4,2=>3,3=>1] After [3=>1,0=>2,2=>3,1=>4]
So now the values are sorted and the index can be used in the next step.
In the last foreach a new array is generated. The index $k from the $sortable_array is used to get the subsarrays from the original_array in the new order.

note: This part if (is_array($v)) makes the function behavior not predictable, because it takes just the $v if $v is not an subarray else it would take data from the subarray!!!

sorting an array which its values are associate array

6 Answers6