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

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
 * )


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:
    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.

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