PHP 8 reference · Array Functions

PHP array_keys() Function

Return all the keys of an array, or only the keys whose value matches a search value.

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Syntax

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

Parameter	Description
`array`	The input array.
`filter_value` optional	Only return keys for this value.
`strict` optional	`true` compares with `===`. Default: `false`

A list of keys.

All keysTry it yourself

<?php
$user = ["name" => "Ada", "role" => "admin", "active" => true];
print_r(array_keys($user));

Output

Array
(
    [0] => name
    [1] => role
    [2] => active
)

Keys for a valueTry it yourself

<?php
$votes = ["ann" => "yes", "bob" => "no", "cal" => "yes"];
print_r(array_keys($votes, "yes"));

Output

Array
(
    [0] => ann
    [1] => cal
)

Version	Change
PHP 4.0	Added

array_values() · Return all the values of an array as a list re-indexed from 0. Often used after array_filter() or unset().
array_key_exists() · Check whether an array has a given key, even if its value is null. isset() returns false for null values.
array_search() · Search an array for a value and return the first matching key, or false if it isn't there.
array_flip() · Swap keys and values, so each value becomes a key. Values must be strings or integers; duplicates keep the last key.
PHP Arrays · tutorial
PHP Array Functions · tutorial