: str_replace(): Passing null to parameter #2 ($replace) of type array|string is deprecated in
namespace Yoast\WP\SEO\Helpers;
* Flattens a multidimensional array of settings. Recursive.
* @param array $array_to_flatten The array to be flattened.
* @param string $key_prefix The key to be used as a prefix.
* @return array The flattened array.
public function flatten_settings( $array_to_flatten, $key_prefix = '' ) {
foreach ( $array_to_flatten as $key => $value ) {
if ( \is_array( $value ) ) {
$result = \array_merge( $result, $this->flatten_settings( $value, $key_prefix . '/' . $key ) );
$result[ $key_prefix . '/' . $key ] = $value;