PHP: array_key_first - Manual
(PHP 7 >= 7.3.0, PHP 8)
array_key_first — Gets the first key of an array
Description
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:
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_first() - Gets the first value of an array
- array_key_last() - Gets the last key of an array
- reset() - Set the internal pointer of an array to its first element
Found A Problem?
MaxiCom dot Developpement at gmail dot com ¶
2 years 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));
?>