Usage and Examples of PHP array_change_key_case() Function

PHP Array Functions

Definition and Usage

array_change_key_case()The function changes the case of all keys in the passed array and returns an array with all keys in lowercase or uppercase depending on the option passed.

By default, this function returns an array with lowercase keys.

Syntax

array array_change_key_case(array $input[, int $case])

Parameter

Return Value

The PHP array_change_key_case() function returns an array whose keys are in lowercase or uppercase form; if the input passed is not a valid PHP array, it returnsFALSE.

PHP version

This function was originally introduced in PHP version4.2introduced in version 5.2.0.

Online Example

Try the following example where we will convert all keys to uppercase-

<?php
　　　$input = array("FirSt"=>　10, "SecOnd" =>　400, "Third" =>　800, );
　　　print_r(array_change_key_case($input, CASE_UPPER));
?>

Output Result

Array
(
　　　　[FIRST] =>　10
　　　　[SECOND] =>　400
　　　　[THIRD] =>　800
)

Online Example

The following example will convert all keys to lowercase-

<?php
　　　$input = array("FirSt"=>　10, "SecOnd" =>　400, "Third" =>　800, );
　　　print_r(array_change_key_case($input, CASE_LOWER));
?>

Output Result

Array
(
　　　　[first] =>　10
　　　　[second] =>　400
　　　　[third] =>　800
)

Online Example

Let's check how it will work by default if we do not pass the second option in the function-

<?php
　　　$input = array("FirSt"=>　10, "SecOnd" =>　400, "Third" =>　800, );
　　　print_r(array_change_key_case($input));
?>

Output Result

Array
(
　　　　[first] =>　10
　　　　[second] =>　400
　　　　[third] =>　800
)

Online Example

The following example returns FALSE and issues a warning because we are trying to pass a simple PHP string instead of a PHP array-

<?php
　　　$input = "This is a string";
　　　print_r(array_change_key_case($input, CASE_LOWER));
?>

This will not produce any output, but will display the following warning. If you want to check the return value of the function, it will be FALSE-

PHP Warning: array_change_key_case() expects parameter　1　to be array, string given in main.php on line　3

PHP Array Functions