Array Change Key Case

Array Change Key Case (array_change_key_case) is a simple function THAT allows you to make all the keys of your array uppercase or lowercase.

• Basic Example
• Composition
• Features and Specific Examples
• Further Reading

Basic Example

If we setup an array with uppercase keys (line 1), we can use the array_change_key_case function to make all of these keys lowercase (line 5).

This gives us the same array back, but with all the keys lowercase.

$array = [
    'P' => 42,
    'POST_STATUS' => 'publish',
];
$lower_case_array = array_change_key_case( $array, CASE_LOWER );
print_r( $lower_case_array ); // Output the new array.

/**
 * Output:
 *
 * Array
 * (
 *    [p] => 42
 *    [post_status] => publish
 * )
 **/

Composition

array_change_key_case( $array, $case );

The function accepts two parameters. The $array you want to change, and the $case (optional, CASE_LOWER by default) that you want the keys to be transformed to. These are as follows:

1. The $array parameter accepts an array, and is the initial array that we we wish to transform.
2. The $case parameter accepts an integer, which is inputted using one of the two PHP predefined constants:
   1. CASE_UPPER
   2. CASE_LOWER (default)

Features and Specific Examples

Changing the Case of Object Keys

In PHP you can easily cast Objects as Arrays and vice-versa, so with that logic you can transform the keys of an Object with array_change_key_case simply by casting the object to an array and back again.

$object              = new StdClass();
$object->ID          = 42;
$object->POST_STATUS = 'publish';
$lower_case_object   = (object) array_change_key_case( (array) $object, CASE_LOWER );
print_r( $lower_case_object ); // Output the new Object.

/**
 * Output:
 * stdClass Object
 * (
 *    [id] => 42
 *    [post_status] => publish
 * )
 **/

In the above example we create an object with uppercase keys, and then transform it to use lowercase keys.

Further Reading

For more reading you can checkout the PHP manual.