Notice!
$a = array(
1 => 1,
0 => 0
);
echo (array_key_last($a)); // output: "0", not "1"
(PHP 7 >= 7.3.0, PHP 8)
array_key_last — 获取一个数组的最后一个键值
array要操作的数组。
返回 array 的最后一个键值（如果不为空），否则返回 null。
Notice!
$a = array(
1 => 1,
0 => 0
);
echo (array_key_last($a)); // output: "0", not "1"
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;
}
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().
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),
]
// if : php ver < 7
// array_key_last
$arr = array('1'=>'bear1','2'=>array('22'=>'bear22'),'3'=>'bear3');
echo end(array_keys($arr));
// result : 3
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;
}
}
?>
<?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
?>
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;
}
?>
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));
}
}
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));
}
}
?>
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 $key;
}
}
?>
For PHP <= 7.3.0 :
if (! function_exists("array_key_last")) {
function array_key_last($array) {
if (!is_array($array) || empty($array)) {
return NULL;
}
return array_keys($array)[count($array)-1];
}
}