PHP 7.2.0 Beta 1 Released

Sorting Arrays

PHP has several functions that deal with sorting arrays, and this document exists to help sort it all out.

The main differences are:

  • Some sort based on the array keys, whereas others by the values: $array['key'] = 'value';
  • Whether or not the correlation between the keys and values are maintained after the sort, which may mean the keys are reset numerically (0,1,2 ...)
  • The order of the sort: alphabetical, low to high (ascending), high to low (descending), numerical, natural, random, or user defined
  • Note: All of these sort functions act directly on the array variable itself, as opposed to returning a new sorted array
  • If any of these sort functions evaluates two members as equal then the order is undefined (the sorting is not stable).

Sorting function attributes
Function name Sorts by Maintains key association Order of sort Related functions
array_multisort() value associative yes, numeric no first array or sort options array_walk()
asort() value yes low to high arsort()
arsort() value yes high to low asort()
krsort() key yes high to low ksort()
ksort() key yes low to high asort()
natcasesort() value yes natural, case insensitive natsort()
natsort() value yes natural natcasesort()
rsort() value no high to low sort()
shuffle() value no random array_rand()
sort() value no low to high rsort()
uasort() value yes user defined uksort()
uksort() key yes user defined uasort()
usort() value no user defined uasort()

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User Contributed Notes 5 notes

"Matthew Rice"
4 years ago
While this may seem obvious, user-defined array sorting functions ( uksort(), uasort(), usort() ) will *not* be called if the array does not have *at least two values in it*.

The following code:                       


function usortTest($a, $b) {
    return -

$test = array('val1');
usort($test, "usortTest");

$test2 = array('val2', 'val3');
usort($test2, "usortTest");


Will output:

string(4) "val3"
string(4) "val2"

The first array doesn't get sent to the function.

Please, under no circumstance, place any logic that modifies values, or applies non-sorting business logic in these functions as they will not always be executed.
oculiz at gmail dot com
6 years ago
Another way to do a case case-insensitive sort by key would simply be:

($array, 'strcasecmp');

Since strcasecmp is already predefined in php it saves you the trouble to actually write the comparison function yourself.
Hayley Watson
10 months ago
Stabilizing the sort functions (in this case, usort).

function stable_usort(&$array, $cmp)
$i = 0;
$array = array_map(function($elt)use(&$i)
        return [
$i++, $elt];
usort($array, function($a, $b)use($cmp)
$cmp($a[1], $b[1]) ?: ($a[0] - $b[0]);
$array = array_column($array, 1);

Tags each array element with its original position in the array so that when the comparison function returns 0 the tie can be broken to put the earlier element first.
monicse09ku at yahoo dot com
2 years ago
// takes an array and desired key value and returns an array
// searches through an array for a given key, if found the key that row is made the first row and the other rows are inserted accordingly.
// the facility of this function is to get the value with a specific key of an array as the first value.

/////////////////////////////// function starts //////////////////////////////

function dksort($array, $case){
        $a[$case] = $array[$case];
        foreach($array as $key=>$val){

                $a[$key] = $array[$key];

    return $a;

$d = array(

$c = dksort($d, '55');

////////////////////////// function ends ////////////////////////////////////////
2 years ago
simple example sorting dotted version numbers

     function sortByVersionnumber($a,$b){
         $ta=explode(".",$a); $tb=explode(".",$b);
         foreach ($ta as $k => $v){
             if (isset($tb[$k])){
                 if($ta[$k] > $tb[$k]) {
                     return 1;
                 } elseif($ta[$k] < $tb[$k]) {
                     return -1;
         return 0;
     function vnksort(&$array){
         uksort($array ,"sortByVersionnumber");
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