PHP: array_keys() function

Last update on August 19 2022 21:50:39 (UTC/GMT +8 hours)

PHP: Return all the keys of an array

The array_keys() function is used to get all the keys or a subset of the keys of an array.

Version:

(PHP 4 and above)

Syntax:

array_keys(input_array, search_key_value, strict)

Note: If the optional search_key_value is specified, then only the keys for that value are returned. Otherwise, all the keys from the array are returned.

Parameters:

Name	Description	Required / Optional	Type
input_array	Specified array.	Required	Array
search_key_value	Value to be checked.	Optional	Array
strict	As of PHP 5, this parameter determines if strict comparison (===) should be used during the search.	Optional	Boolean

Return value:

An array of all the keys of input_arrray.

Value Type: Array

Example - 1:

<?php
$array1=array("Orange" => 100, "Apple" => 200, "Banana" => 300, "Cherry" => 400);
print_r(array_keys($array1));
?>

Output:

Array ( [0] => Orange [1] => Apple [2] => Banana [3] => Cherry )

Pictorial Presentation:

php function reference: array_keys() function

View the example in the browser

Example - 2 :

<?php
$array1=array("Orange","Apple","Banana","Apple");
print_r(array_keys($array1,"Apple"));
?>

Output :

Array ( [0] => 1 [1] => 3 )

View the example in the browser

Practice here online :

See also

PHP Function Reference

Previous:array_key_exists
Next: array_map

PHP: Tips of the Day

Filters the collection using the given callback

Example:

<?php
function tips_reject($items, $func)
{
  return array_values(array_diff($items, array_filter($items, $func)));
}

print_r(tips_reject(['Apple', 'Pear', 'Kiwi', 'Banana'], function ($item) {
  return strlen($item) > 4;
}));
?>

Output:

Array
(
    [0] => Pear
    [1] => Kiwi
)