* @param $stackName Name of the stack
* @return $stackInstance An instance of a StackableFile class
*/
- public static final function createFileStackInstance ($prefix, $stackName) {
+ public static final function createFileStackInstance (string $prefix, string $stackName) {
// Construct file stack name
$fileInfoInstance = new SplFileInfo(sprintf('%s%s/%s.%s',
FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('root_base_path'),