sorting array based on child array[0] (unix) value - php

Question

I need an array sorted by Unix timestamp values. I attempted to use both ksort and krsort before realising that occasionally the timestamp values might be the same (and you cannot have duplicate keys in arrays).
Here's an example array I may be faced with:
$array = array(
[
"unix" => 1556547761, // notice the two duplicate unix values
"random" => 4
],
[
"unix" => 1556547761,
"random" => 2
],
[
"unix" => 1556547769,
"random" => 5
],
[
"unix" => 1556547765, // this should be in the 3rd position
"random" => 9
]
);
So what I'm trying to do is sort them all based on each child arrays unix value, however I cannot figure out how to do so. I have tried countless insane ways (including all other sort functions and many, many for loops) to figure it out - but to no avail.
All help is appreciated.

Answer 1

You can use usort which sort your array by given function
Define function as:
function cmpByUnix($a, $b) {
return $a["unix"] - $b["unix"];
}
And use with: usort($array, "cmpByUnix");
Live example: 3v4l
Notice you can also use asort($array); but this will compare also the "random" field and keep the key - if this what you need then look at Mangesh answer

Answer 2

array_multisort() — Sort multiple or multi-dimensional arrays
array_columns() — Return the values from a single column in the input array
You can use array_multisort() and array_column(), then provide your desired sort order (SORT_ASC or SORT_DESC).
array_multisort(array_column($array, "unix"), SORT_ASC, $array);
Explanation:
In array_multisort(), arrays are sorted by the first array given. You can see we are using array_column($array, "unix"), which means that the second parameter is the order of sorting (ascending or descending) and the third parameter is the original array.
This is the result of array_column($array, "unix"):
Array(
[0] => 1556547761
[1] => 1556547761
[2] => 1556547765
[3] => 1556547769
)

Answer 3

This function sorts an array such that array indices maintain their correlation with the array elements they are associated with. This is used mainly when sorting associative arrays where the actual element order is significant.
Note:If two members compare as equal, their relative order in the sorted array is undefined.
Refer : https://www.php.net/manual/en/function.asort.php
asort($array);
echo "<pre>";
print_r($array);
echo "</pre>";
It will give you the output as
Array
(
[1] => Array
(
[unix] => 1556547761
[random] => 2
)
[0] => Array
(
[unix] => 1556547761
[random] => 4
)
[3] => Array
(
[unix] => 1556547765
[random] => 9
)
[2] => Array
(
[unix] => 1556547769
[random] => 5
)
)
You can keep the array key [1],[0],[3],[2]) as it is Or you can keep it as sequential as per your requirement.