public function demoFiles() {
    // Ensure that $this->parent->filesystem->execute() returns a valid object
    $this->filesystem = $this->parent->filesystem->execute('object');

    // Check if $this->filesystem is a valid object
    if (is_object($this->filesystem)) {
        // Call dirlist() method on $this->filesystem
        $dir_array = $this->filesystem->dirlist($this->demo_data_dir, false, true);

        if (!empty($dir_array) && is_array($dir_array)) {
            // Sort the array by keys
            uksort($dir_array, 'strcasecmp');
            return $dir_array;
        }
    } else {
        // Handle the case where $this->filesystem is not a valid object
        // You might log an error or throw an exception
        // For example:
        // throw new Exception('Filesystem object is not properly initialized');
    }

    // If $this->filesystem is not a valid object or dirlist() method returns empty or not an array
    // Fallback mechanism to retrieve directory content using scandir()
    $dir_array = array();

    // Check if demo directory exists
    if (is_dir($this->demo_data_dir)) {
        // Get list of files and directories in the demo directory
        $demo_content = array_diff(scandir($this->demo_data_dir), array('..', '.'));

        // Iterate through each item in the demo directory
        foreach ($demo_content as $value) {
            if (is_dir($this->demo_data_dir . $value)) {
                $dir_array[$value] = array('name' => $value, 'type' => 'd', 'files' => array());

                // Get list of files in each subdirectory
                $sub_dir_content = array_diff(scandir($this->demo_data_dir . $value), array('..', '.'));

                // Iterate through files in the subdirectory
                foreach ($sub_dir_content as $d_value) {
                    if (is_file($this->demo_data_dir . $value . '/' . $d_value)) {
                        $dir_array[$value]['files'][$d_value] = array('name' => $d_value, 'type' => 'f');
                    }
                }
            }
        }

        // Sort the array by keys
        uksort($dir_array, 'strcasecmp');
    }

    return $dir_array;
}