PHP array_​key_​first() Function

The array_​key_​first() function is an inbuilt function in PHP that is used to get the first key of an array. This function returns the first key without affecting the internal array pointer.

Syntax:

int|string|null array_key_first(array $array)

Parameters: This function accepts a single parameter $array that holds the array.

Return Value: This function returns the first key of the array if the array is not empty, and null otherwise.

Example 1:

PHP

<?php

$arr = array();

var_dump(array_key_first($arr));

$arr1 = array("10", "20", "30", "40", "50");
var_dump(array_key_first($arr1));

?>

Output:

NULL
int(0)

Example 2:

PHP

<?php

$arr = array(
    'Geeks'  => "HTML",
    'GFG'  => "CSS",
    'Geek'  => "JavaScript",
    'G4G' => "PHP"
);

var_dump(array_key_first($arr));

$arr1 = array(
    5 => "geeks",
    10 => "GFG"
);

var_dump(array_key_first($arr1));

?>

Output:

string(5) "Geeks"
int(5)

Reference: https://www.php.net/manual/en/function.array-key-first.php