php实现单例模式原理

单例模式：

class Single{public $rand;static public $ob = null;final private function __construct(){$this->rand = mt_rand(100000,99999999);}static public function getobj(){       if(Single::$ob === null){          Single::$ob = new Single();       }       return Single::$ob;}}var_dump(Single::getobj());var_dump(Single::getobj());