array_key_first

    (PHP 7 >= 7.3.0, PHP 8)

    array_key_first — Gets the first key of an array

    Опис

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

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

    Параметри

    array

    An array.

    Значення, що повертаються

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

    Приклади

    Приклад #1 Basic array_key_first() Usage

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

    $firstKey = array_key_first($array);

    var_dump($firstKey);
    ?>

    Поданий вище приклад виведе:

    string(1) "a"

    Примітки

    Підказка

    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;
    }
    }
    ?>

    Прогляньте також

    • array_key_last() - Gets the last key of an array
    • reset() - Встановлює внутрішній вказівних масиву на його перший елемент

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    User Contributed Notes 1 note

    up
    2
    MaxiCom dot Developpement at gmail dot com
    10 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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