/** Restore an instance of this class to be the current instance.
*
* This should only be used if you <em>really</em> know what you're doing,
* as it messes with the internals of this class, and is meant for internal
* use only, to implement some functionality needed in the absence of ESI.
* @param nxcESIEAS|null $instance The instance to restore as the current
* instance, or null to reset the class so a new instance is created.
* @return nxcESIEAS|null|false The previous instance of this class, or
* null if no previous instance existed, or false on error.
* A returned instance should be treated as an opaque handle, not used for
* anything except later calls to this method, for internal state reasons.
* @see instance()
*/
public static function restoreInstance($instance)
{
if ($instance instanceof self) {
$previousInstance = self::$instance;
self::$instance = $instance;
$instance->updateSurrogateControlHeader();
if ($previousInstance instanceof self) {
return $previousInstance;
}
return null;
}
return false;
}
