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array_keys

Return all the keys of an array (PHP 4, PHP 5)
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 (===).

Parameters

input

An array containing keys to return.

search_value

If specified, then only keys containing these values are returned.

strict

As of PHP 5, this parameter determines if strict comparision (===) should be used during the search.

Return Values

Returns an array of all the keys in input.

Examples

Example 256. 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
)