php[world] 2019 — 25 years of PHP

array_key_first

(PHP 7 >= 7.3.0)

array_key_firstGets the first key of an array

Descrição

array_key_first ( array $array ) : mixed

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

Parâmetros

array

An array.

Valor Retornado

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

Exemplos

Exemplo #1 Basic array_key_first() Usage

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

$firstKey array_key_first($array);

var_dump($firstKey);
?>

O exemplo acima irá imprimir:

string(1) "a"

Notas

Dica

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;
    }
}
?>

Veja Também

  • array_key_last() - Gets the last key of an array
  • reset() - Faz o ponteiro interno de um array apontar para o seu primeiro elemento
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