array_key_first

    (PHP 7 >= 7.3.0, PHP 8)

    array_key_first — Gets the first key of an array

    Descrizione

    array_key_first(array $array): int|string|null

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

    Elenco dei parametri

    array

    An array.

    Valori restituiti

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

    Esempi

    Example #1 Basic array_key_first() Usage

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

    $firstKey = array_key_first($array);

    var_dump($firstKey);
    ?>

    Il precedente esempio visualizzerà:

    string(1) "a"

    Note

    Suggerimento

    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;
    }
    }
    ?>

    Vedere anche:

    • array_key_last() - Gets the last key of an array
    • reset() - Reimposta il puntatore interno di un array sulla posizione iniziale

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    User Contributed Notes 1 note

    up
    2
    MaxiCom dot Developpement at gmail dot com
    11 months ago
    A polyfill serves the purpose of retroactively incorporating new features from PHP releases into older PHP versions, ensuring API compatibility.

    In PHP 7.3.0, the array_key_first() function was introduced, demonstrated in the following example:

    <?php

    $array     = [
    'first_key' => 'first_value',
    'second_key' => 'second_value',
    ];

    var_dump(array_key_first($array));

    ?>

    The provided polyfill in this documentation allows the convenient use of array_key_first() with API compatibility in PHP versions preceding PHP 7.3.0, where the function was not implemented:

    <?php

    if (!function_exists('array_key_first')) {
    function     array_key_first(array $arr) {
    foreach (    $arr as $key => $unused) {
    return     $key;
    }
    return     null;
    }
    }

    $array = [
    'first_key' => 'first_value',
    'second_key' => 'second_value',
    ];

    var_dump(array_key_first($array));

    ?>
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