/**
* Set backend value
*
* @param FileRepository_Backend $value
* @return null
* @throws InvalidInstanceError
*/
static function setBackend($value, $backend_name = null)
{
if ($value instanceof FileRepository_Backend) {
if (is_null($backend_name)) {
self::$default_backend = $value;
} else {
self::$additional_backends[$backend_name] = $value;
}
// if
} else {
throw new InvalidInstanceError('value', $value, 'FileRepository_Backend');
}
// if
}
