PHP开发APP接口----单例模式连接数据库

<?php
//单例模式
 class Db{
       static private $_instance;
       static private $_connectSource;
       private $_dbConfig=array(
           'host'=>'localhost',
           'user'=>'root',
           'passward'=>'111',
           'database'=>'db_database12',
       );
       private function __construct(){  
      } 
      static public function getInstance(){ //相当于单例模式的一个入口
          if(!(self::$_instance instanceof self)){  //instanceof:它的作用是判断其左边对象是否为其右边类的实例，返回boolean类型的数据。
          self::$_instance=new self();
          }    
          return self::$_instance;
      }
      public function connect(){
          if(!self::$_connectSource){
                self::$_connectSource=  mysql_connect($this->_dbConfig['host'],$this->_dbConfig['user'],$this->_dbConfig['passward']);
                if(!self::$_connectSource){
                    die('mysql connect error'.mysql_error());
                }  
                mysql_select_db($this->_dbConfig['database'],self::$_connectSource);
                mysql_query('set names gbk',self::$_connectSource);
          }
                return self::$_connectSource;
      }
 }
   $connect= Db::getInstance()->connect();
   $sql="select *from tb_demo01";
   $result=mysql_query($sql,$connect);     --------------》》》》 $arry=array();
   $arr=mysql_fetch_row($result);                                while($arr=mysql_fetch_row($result)){                      
   var_dump($arr);                                               $arry[]=$arr;
                                                                 }
                                                                    var_dump($arry);