工厂方法模式

factory模式
定义一个用于创建对象的接口,让子类决定将哪一个类实例化,使用一个类的实例化延迟到其子类,实例1是传统模式，实例2是工厂方法。

    class DBFactory
    {
        public static function create($type)
        {
            swtich ($type) {
                case "Mysql":
                    return new MysqlDB(); break;
                case "Postgre":
                    return new PostgreDB(); break;
                case "Mssql":
                    return new MssqlDB(); break;
            }
        }
    }

class DBFactory
{
    public static function create($type)
    {
        $class = $type."DB";
        return new $class;
    }
}

interface DB
{
    public function connect();
    public function exec();
}

class MysqlDB implements DB
{
    public function __construct()
    {
        echo"mysql db
";
    }
    public function connect(){ }
    public function exec(){ }
}

class PostgreDB implements DB
{
    public function __construct()
    {
        echo"Postgre db
";
    }
    
    public function connect(){ }
    
    public function exec(){ }
}

class MssqlDB implements DB
{
    public function __construct()
    {
        echo"mssql db
";
    }
    public function connect() { }
    public function exec() { }
}

$oMysql = DBFactory::create("Mysql");
$oPostgre = DBFactory::create("Postgre");
$oMssql = DBFactory::create("Mssql");

参考文章 https://wenku.baidu.com/view/b4c78b4702768e9951e738fb.html