public static function getInstance(
        $root_dir = null, $assets_dir = null, $document_root = null, $conflict_flag = self::PRESETS_CONFLICT
    ) {
        if (empty(self::$__instance)) {
            $cls = get_called_class();
            self::$__isStaticInstance = true;
            self::$__instance = new $cls($root_dir, $assets_dir, $document_root, $conflict_flag);
        }
        return self::$__instance;
    }
public static function getInstance(
        $root_dir = null, $assets_dir = null, $document_root = null, $conflict_flag = self::PRESETS_CONFLICT
    ) {
        if (empty(self::$__instance)) {
            $cls = get_called_class();
            self::$__isStaticInstance = true;
            self::$__instance = new $cls($root_dir, $assets_dir, $document_root, $conflict_flag);
        }
        return self::$__instance;
    }
public static function getInstance ( $ root_dir = null , $ assets_dir = null , $ document_root = null , $ conflict_flag = self :: PRESETS_CONFLICT ) { if ( empty ( self :: $ __instance ) ) { $ cls = get_called_class ( ) ; self :: $ __isStaticInstance = true ; self :: $ __instance = new $ cls ( $ root_dir , $ assets_dir , $ document_root , $ conflict_flag ) ; } return self :: $ __instance ; }
Loader static instance constructor

@param   string  $root_dir       The project package root directory
@param   string  $assets_dir     The project package assets directory, related from `$root_dir`
@param   string  $document_root  The project assets root directory to build web accessible assets paths
@param   int     $conflict_flag  Define if the class must throw exceptions in case of presets conflicts
@return  self
Loader static instance constructor