sorting an array which its values are associate array - php

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?

Answer 1

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.

Answer 2

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");

Answer 3

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
)
)

Answer 4

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);

Answer 5

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
)
)

Answer 6

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!!!