/**
* Ensure that only one instance of the maintenance tracker exists and returns it
* @return MaintenanceTracker The maintenance tracker instance
*/
public static function getMaintenanceTracker()
{
if (MaintenanceTracker::$maintenanceTracker === null) {
//if it has not been created
MaintenanceTracker::$maintenanceTracker = new MaintenanceTracker();
}
//create
return MaintenanceTracker::$maintenanceTracker;
}
