array_key_first

(PHP 7 >= 7.3.0)

array_key_firstGets the first key of an array

Opis

array_key_first ( array $array ) : mixed

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
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