class?Database?{
????private?static?$instance?=?null;
????
????private?function?__construct(){

????}
????
????//?這里使用static進行后期靜態綁定，繼承該類，即可變身為單例
????public?static?function?getInstance(){
????????if(!(static::$instance===null)){
????????????static::$instance?=?new?static;
????????}
????????
????????return?static::$instance;
????}
????
????private?function?__clone(){

????}
????
???//其他成員
}