<?php
class Config{
    static private $_instance = null; //确保对于一个特定类来说只存在一个单一的实例
    private $_settings = array();
    
    private function __construct(){}//防止new出来一个新实例
    private function __clone(){} //防止clone来创建一个新实例

    static funcitn getInstance(){
          if(self::$_instance == null){
              self::$_instance = new Config();
          }
          return self::$_instance;
    }

    function set($index, $value){
         $this->_settings[$index] = $value;
   }

    function get($index){
          return $this->_settings[$index];
    }
}
?>