public function createFolder($parentFolderPath, $folderName)
{
$this->throwIfOperationNotInBaseFolder($parentFolderPath);
$folderPath = $parentFolderPath . '/' . $folderName;
$wasCreationSuccessful = mkdir($folderPath, 0777, true);
if (!$wasCreationSuccessful) {
throw new IOException("Unable to create folder: {$folderPath}");
}
return $folderPath;
}