Grav\Plugin\Admin\AdminBaseController::storeFiles PHP Method

    protected function storeFiles($obj)
    {
        // Process previously uploaded files for the current URI
        // and finally store them. Everything else will get discarded
        $queue = $this->admin->session()->getFlashObject('files-upload');
        $queue = $queue[base64_encode($this->grav['uri']->url())];
        if (is_array($queue)) {
            foreach ($queue as $key => $files) {
                foreach ($files as $destination => $file) {
                    if (!rename($file['tmp_name'], $destination)) {
                        throw new \RuntimeException(sprintf($this->admin->translate('PLUGIN_ADMIN.FILEUPLOAD_UNABLE_TO_MOVE', null), '"' . $file['tmp_name'] . '"', $destination));
                    }
                    unset($files[$destination]['tmp_name']);
                }
                if ($this->view == 'pages') {
                    $keys = explode('.', preg_replace('/^header./', '', $key));
                    $init_key = array_shift($keys);
                    if (count($keys) > 0) {
                        $new_data = isset($obj->header()->{$init_key}) ? $obj->header()->{$init_key} : [];
                        Utils::setDotNotation($new_data, implode('.', $keys), $files, true);
                    } else {
                        $new_data = $files;
                    }
                    if (isset($data['header'][$init_key])) {
                        $obj->modifyHeader($init_key, array_replace_recursive([], $data['header'][$init_key], $new_data));
                    } else {
                        $obj->modifyHeader($init_key, $new_data);
                    }
                } else {
                    // TODO: [this is JS handled] if it's single file, remove existing and use set, if it's multiple, use join
                    $obj->join($key, $files);
                    // stores
                }
            }
        }
        return $obj;
    }