php[world] 2019 — 25 years of PHP

array_key_first

(PHP 7 >= 7.3.0)

array_key_firstGets the first key of an array

Descripción

array_key_first ( array $array ) : mixed

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

Parámetros

array

An array.

Valores devueltos

Returns the first key of array if the array is not empty; NULL otherwise.

Ejemplos

Ejemplo #1 Basic array_key_first() Usage

<?php
$array 
= ['a' => 1'b' => 2'c' => 3];

$firstKey array_key_first($array);

var_dump($firstKey);
?>

El resultado del ejemplo sería:

string(1) "a"

Notas

Sugerencia

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;
    }
}
?>

Ver también

  • array_key_last() - Gets the last key of an array
  • reset() - Establece el puntero interno de un array a su primer elemento
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