array_key_first
(PHP 7 >= 7.3.0, PHP 8)
array_key_first — Gets the first key of an array
Beschreibung
$array
): int|string|null
Get the first key of the given array
without affecting
the internal array pointer.
Parameter-Liste
-
array
-
An array.
Rückgabewerte
Returns the first key of array
if the array is not empty;
null
otherwise.
Beispiele
Beispiel #1 Basic array_key_first() Usage
<?php
$array = ['a' => 1, 'b' => 2, 'c' => 3];
$firstKey = array_key_first($array);
var_dump($firstKey);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
string(1) "a"
Anmerkungen
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;
}
}
?>
Siehe auch
- array_key_last() - Gets the last key of an array
- reset() - Setzt den internen Zeiger eines Arrays auf sein erstes Element