Array Functions
PHP Manual

array_key_first

Gets the first key of an array

Description

intstringnull array_key_first(array $array)

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

Parameters

array

An array.

Return Values

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

Examples

Example #1 Basic array_key_first Usage

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

$firstKey = array_key_first($array);

var_dump($firstKey);
?>

The above example will output:

string(1) "a"

Notes

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;
    }
}
?>

See Also

  • array_key_last
  • reset