public static function main(array $args = array())
 {
     $boiler = ChocolateBoiler::getInstance();
     $boiler->fill();
     $boiler->boil();
     $boiler->drain();
     // will return the existing instance
     $boiler2 = ChocolateBoiler::getInstance();
 }
 public static function getInstance()
 {
     if (self::$uniqueInstance == NULL) {
         println("Creating unique instance of Chocolate Boiler");
         self::$uniqueInstance = new ChocolateBoiler();
     }
     println("Returning instance of Chocolate Boiler");
     return self::$uniqueInstance;
 }