PHP 7.4.0RC6 Released!

array_key_first

(PHP 7 >= 7.3.0)

array_key_firstGets the first key of an array

说明

array_key_first ( array $array ) : mixed

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

参数

array

An array.

返回值

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

范例

Example #1 Basic array_key_first() Usage

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

$firstKey array_key_first($array);

var_dump($firstKey);
?>

以上例程会输出:

string(1) "a"

注释

Tip

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;
    }
}
?>

参见

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User Contributed Notes 1 note

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1
webmaster at redinfo dot co dot kr
1 month ago
// if : php > 7
$arr = array('a'=>'apple','b'=>'bone','c'=>'company');
echo current(array_keys($arr));

// result: a
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