A proper one-liner polyfill for version < 7.3:
<?php
function array_key_first((array) $a)
{
return array_keys($a)[0];
}
array_key_first
(PHP 7 >= 7.3.0)
array_key_first — Gets the first key of an array
Opis
Get the first key of the given array without affecting
the internal array pointer.
Parametry
-
array -
An array.
Zwracane wartości
Returns the first key of array if the array is not empty;
NULL otherwise.
Przykłady
Przykład #1 Basic array_key_first() Usage
<?php
$array = ['a' => 1, 'b' => 2, 'c' => 3];
$firstKey = array_key_first($array);
var_dump($firstKey);
?>
Powyższy przykład wyświetli:
string(1) "a"
Notatki
Wskazówka
There are several ways to provide this functionality for versions prior to PHP 7.3.0. It is possible to use array_keys(), but that may be rather inefficient. It is also possible to use reset() and key(), but that may change the internal array pointer. An efficient solution, which does not change the internal array pointer, written as polyfill:
<?php
if (!function_exists('array_key_first')) {
function array_key_first(array $arr) {
foreach($arr as $key => $unused) {
return $key;
}
return NULL;
}
}
?>
Zobacz też:
- array_key_last() - Gets the last key of an array
- reset() - Ustaw wewnętrzny wskaźnik tablicy na jej pierwszy element
add a note
User Contributed Notes 3 notes
nekto at nekto dot com dot ua ¶
2 years ago
Vee W. ¶
3 years ago
Another way to get first array key with PHP older than 7.3.
<?php
$array = ['one', 'two', 'three'];
$array2 = ['one' => 'Number one', 'two' => 'Number two'];
reset($array);// go to first array
echo key($array);// get its key (first array)
// expect 0.
reset($array2);
echo key($array2);
// expect one.
github.com / ahsankhatri ¶
3 years ago
One-liner polyfill (php version < 7.3.0)
<?php
function array_key_first(array $array)
{
return key(array_slice($array, 0, 1));
}
