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# array_keys

(PHP 4, PHP 5)

array_keys -- Return all the keys of an array

## Description

array array_keys ( array input [, mixed search_value [, bool strict]] )

array_keys() returns the keys, numeric and string, from the `input` array.

If the optional `search_value` is specified, then only the keys for that value are returned. Otherwise, all the keys from the `input` are returned. As of PHP 5, you can use `strict` parameter for comparison including type (===).

Example 1. array_keys() example

`<?php $array = array(0 => 100, "color" => "red"); print_r(array_keys($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)); ?>`

The above example will output:

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

See also array_values() and array_key_exists().

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