PHP array_keys function

PHP array_keys function returns all the keys in a new array; this will be an indexed array. If you use $search_value in the parameters, it will return an array that contains a subset of keys with that value.

array_keys(array $array): array

array_keys(array $array, mixed $search_value, bool $strict = false): array

$narray = array_keys($array_proporcinado);

Parameters

$array – The array that we provide.

$search_value – If this parameter is specified, the returned array will contain only keys that have this value.

$strict – Determines whether to use strict comparison (===).

Return

It will return an array with all the keys from the provided array.

Examples of PHP array_keys function

Suppose we have this multidimensional array taken from an SQL query. In this case, we cannot directly use array_keys on our $users array, but we can use it on one of its elements.

$users = array(
    array(
        'nombre' => 'Juan Pérez',
        'edad' => 25,
        'email' => 'juan@example.com',
    ),
    array(
        'nombre' => 'María Rodríguez',
        'edad' => 30,
        'email' => 'maria@example.com',
    ),
    array(
        'nombre' => 'Carlos Sánchez',
        'edad' => 22,
        'email' => 'carlos@example.com',
    ),
    array(
        'nombre' => 'Luis González',
        'edad' => 28,
        'email' => 'luis@example.com',
    ),
    array(
        'nombre' => 'Ana Martínez',
        'edad' => 35,
        'email' => 'ana@example.com',
    ),
    array(
        'nombre' => 'Laura López',
        'edad' => 29,
        'email' => 'laura@example.com',
    ),
    array(
        'nombre' => 'Pedro Torres',
        'edad' => 27,
        'email' => 'pedro@example.com',
    ),
    array(
        'nombre' => 'Elena Ramírez',
        'edad' => 31,
        'email' => 'elena@example.com',
    ),
    array(
        'nombre' => 'Sofía García',
        'edad' => 26,
        'email' => 'sofia@example.com',
    ),
    array(
        'nombre' => 'Mario Díaz',
        'edad' => 24,
        'email' => 'mario@example.com',
    ),
    array(
        'nombre' => 'Javier Fernández',
        'edad' => 33,
        'email' => 'javier@example.com',
    ),
    array(
        'nombre' => 'Isabel Ortega',
        'edad' => 23,
        'email' => 'isabel@example.com',
    ),
    array(
        'nombre' => 'Rosa Jiménez',
        'edad' => 32,
        'email' => 'rosa@example.com',
    ),
    array(
        'nombre' => 'Diego Silva',
        'edad' => 28,
        'email' => 'diego@example.com',
    ),
    array(
        'nombre' => 'Carolina Castro',
        'edad' => 34,
        'email' => 'carolina@example.com',
    ),
);

print_r(array_keys($users[0]));

Array
(
    [0] => nombre
    [1] => edad
    [2] => email
)

Let’s see an example from php.net

$array = array(0 => 100, "color" => "red");
print_r(array_keys($array));

$array = array("blue", "red", "green", "blue", "blue");
print_r(array_keys($array, "blue"));

$array = array("color" => array("blue", "red", "green"),
               "size"  => array("small", "medium", "large"));
print_r(array_keys($array));

Array
(
    [0] => 0
    [1] => color
)
Array
(
    [0] => 0
    [1] => 3
    [2] => 4
)
Array
(
    [0] => color
    [1] => size
)