\Drupal\Component\Utility\Unicode::caseFlip() will be removed

\Drupal\Component\Utility\Unicode::caseFlip() was used as a preg_replace callback to provide PHP5 implementations of multibyte string methods. In Drupal 8.8.0 we only support PHP7 so these implementations have been removed.

If custom or contributed code is using this method you can re-implement the method in you own code.

  /**
   * Flip U+C0-U+DE to U+E0-U+FD and back. Can be used as preg_replace callback.
   *
   * @param array $matches
   *   An array of matches by preg_replace_callback().
   *
   * @return string
   *   The flipped text.
   */
  public static function caseFlip($matches) {
    return $matches[0][0] . chr(ord($matches[0][1]) ^ 32);
  }