(PHP 7 >= 7.3.0, PHP 8)
array_key_first — Gets the first key of an array
Parametersarray
An array.
Returns the first key of array if the array is not empty; null otherwise.
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 TipThere 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;
}
}
?>
1 year 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:
<?phpif (!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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