ConFoo 2025

array_key_last

(PHP 7 >= 7.3.0, PHP 8)

array_key_lastGets the last key of an array

Descrizione

array_key_last(array $array): int|string|null

Get the last key of the given array without affecting the internal array pointer.

Elenco dei parametri

array

An array.

Valori restituiti

Returns the last key of array if the array is not empty; null otherwise.

Vedere anche:

  • array_key_first() - Gets the first key of an array
  • end() - Sposta il puntatore interno dell'array all'ultimo elemento
add a note

User Contributed Notes 12 notes

up
40
github / k-gun
5 years ago
For those who loves tested candies;

<?php
function array_key_last(array $array) {
// 100000 iters: ~0.068 secs
return key(array_slice($array, -1));
// 100000 iters: ~0.070 secs
return key(array_reverse($array));
// 100000 iters: ~0.088 secs
return array_keys($array)[count($array) - 1] ?? null;
}
?>
up
52
Anyvie at devlibre dot fr
6 years ago
For PHP <= 7.3.0 :

if (! function_exists("array_key_last")) {
function array_key_last($array) {
if (!is_array($array) || empty($array)) {
return NULL;
}

return array_keys($array)[count($array)-1];
}
}
up
11
contact at duzun dot me
5 years ago
Try to beat this polyfill in terms of performance!

<?php
if( !function_exists('array_key_last') ) {
function
array_key_last(array $array) {
if( !empty(
$array) ) return key(array_slice($array, -1, 1, true));
}
}

// Bonus
if (!function_exists('array_key_first')) {
function
array_key_first(array $arr) {
foreach(
$arr as $key => $unused) return $key;
}
}
?>
up
3
williamdes at wdes dot fr
4 years ago
https://www.php.net/manual/fr/function.array-key-last.php#123950

did return the first key of my array only:
"array_keys($array)[count($array) - 1] ?? null" works

I hope the example is fine for everyone else.

My array is:
[
new NameExpression('d', 0),
new NameExpression('f', 0),
new NameExpression('g', 0),
]
up
5
ccb_bc at hotmail dot com
5 years ago
<?php
// PHP >= 7
function _array_key_last(array $array){
return (!empty(
$array)) ? array_keys($array)[count($array)-1] : null;
}
var_dump(_array_key_last(['PHP', 'Javascript', 'Python'])); // 2
?>
up
6
webmaster at redinfo dot co dot kr
5 years ago
// if : php ver < 7
// array_key_last

$arr = array('1'=>'bear1','2'=>array('22'=>'bear22'),'3'=>'bear3');
echo end(array_keys($arr));

// result : 3
up
5
@manzoorwanijk
6 years ago
For PHP < 7.3.0 :

Will work for any type of array

<?php
if ( ! function_exists( 'array_key_last' ) ) {
/**
* Polyfill for array_key_last() function added in PHP 7.3.
*
* Get the last key of the given array without affecting
* the internal array pointer.
*
* @param array $array An array
*
* @return mixed The last key of array if the array is not empty; NULL otherwise.
*/
function array_key_last( $array ) {
$key = NULL;

if (
is_array( $array ) ) {

end( $array );
$key = key( $array );
}

return
$key;
}
}
?>
up
1
dracveg at gmail dot com
3 years ago
Notice!

$a = array(
1 => 1,
0 => 0
);

echo (array_key_last($a)); // output: "0", not "1"
up
0
donaldinou at gmail dot com
4 years ago
Here come my benchmark, and

return key(array_slice($array, -1));

is the my best answer for a polyfill.

<?php

function array_key_last_1(array $array) {
// assert(!empty($array));
return key(array_slice($array, -1));
}

function
array_key_last_2(array $array) {
return
key(array_slice($array, -1, 1, true));
}

function
array_key_last_3(array $array) {
return
key(array_reverse($array));
}

function
array_key_last_4(array $array) {
return
array_keys($array)[count($array) - 1] ?? null;
}

function
array_key_last_5(array $array) {
return
array_keys($array)[count($array) - 1] ?? null;
}

function
array_key_last_6(array $array) {
$copy = array_keys($array);
return
end($copy);
}

$result = array();
$array = range(0, 1000000);

for(
$i=1; $i < 7;$i++) {
$callback = 'array_key_last_' . $i;
$before = microtime(true);
call_user_func_array($callback, array($array));
$after = microtime(true);
$time = ($after-$before);
$result[$callback] = $time;
}

asort($result);
foreach (
$result as $key => $value) {
echo
'[' . $key . ']' . $value . " sec" . PHP_EOL;
}
up
0
rnealxp at yahoo dot com
4 years ago
Now that we have this function, where we once used...
<?php
$idxLast
= count($arr) - 1;
?>
we can now optimize code speed by using...
<?php
$idxLast
= (array_key_last($arr) ?? 0);
?>
Use-cases include lots of looping and control-structures.
If you do not know ahead of time that the array is numerically indexed, and that it could possibly be associative...safer/faster to stick with count().
up
0
rotexdegba007-github at yahoo dot ca
5 years ago
This polyfill works for PHP 5.6+.
It is a slight modification of "wes at nospam dot example dot org"'s example:

<?php

if( !function_exists('array_key_first') ) {

function
array_key_first(array $array) {

if(
$array === [] ) { return NULL; }

foreach(
$array as $key => $_) { return $key; }
}
}

if( !
function_exists('array_key_last') ) {

function
array_key_last(array $array) {

if(
$array === [] ) { return null; }

// the last 2 args to array_slice are crucial
return array_key_first(array_slice($array, -1, null, true));
}
}
up
-2
wes at nospam dot example dot org
5 years ago
Correct polyfill (one that doesn't make copies of arrays, and that doesn't make use of the IAP) is:

<?php

if(!function_exists('array_key_first')){
function
array_key_first(array $array){
if(
$array === []){
return
NULL;
}
foreach(
$array as $key => $_) return $key;
}
}

if(!
function_exists('array_key_last')){
function
array_key_last(array $array){
if(
$array === []){
return
NULL;
}
return
array_key_first(array_slice($array, -1));
}
}

?>
To Top