PHP单例模式高级用法

class OA {

    public static $oa = array();
    public static $config = array();

    public static function setConfig(array $config) {
        return self::$config = array_merge(self::$config, $config);
    }

    public static function user() {
        if (!key_exists('user', self::$oa) || !is_object(self::$oa['user'])) {
            //引入user.class.php
            self::$oa['user'] = new user();
        }
        return self::$oa['user'];
    }

　　public static function goods() {
        if (!key_exists('user', self::$oa) || !is_object(self::$oa['goods'])) {
            //引入goods.class.php
            self::$oa['goods'] = new goods(); 
        } 
        return self::$oa['goods']; 
    }
}

//加载配置文件
OA::$config = array('dbname'=>'localhost','dbuser'=>'root','dbpassword'=>'123456');
OA::user()->get();
OA::goods()->set();