array_key_first

Gets the first key of an array

&reftitle.description; ``int``string``null```array_key_first` `array` `array`

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

&reftitle.parameters;

`array`

- An array.

&reftitle.returnvalues;

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

&reftitle.examples;

### Basic `array_key_first` Usage

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

    $firstKey = array_key_first($array);

    var_dump($firstKey);
    ?>

&example.outputs;

    string(1) "a"

&reftitle.notes;

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;
        }
    }
    ?>

&reftitle.seealso;

- `array_key_last`
- `reset`