PHP array_keys function

It 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.

Ejemplos

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
)