php工厂方法

<?php 
        interface db{
              function conn();
          }
        interface Factory{
            function createDB();
        } 
        class dbmysql implements db{
            public function conn(){
                echo "连上了mysql数据库";
            }
        }
        class dbsqlite implements db{
            public function conn(){
                echo "连上了dbsqlite数据库";
            }
        }
        class  mysqlFactory implements Factory{
               public function createDB(){
                return new dbmysql();
               }
        }
        class  sqliteFactory implements Factory{
              public function createDB(){
                return new dbsqlite();
              }
        }
        //添加数据库oracle
        class dboracle implements db{
            public function conn(){
                echo "连接上了oracle数据库";
            }
        }
        class oracleFactory implements Factory{
            public function createDB(){
                return new  dboracle();
            }
        }

        //客户端开始
        $fact=new mysqlFactory();
        $db=$fact->createDB();
        $db->conn();