注册模式

$db = \IMooc\Register::get(‘db1‘);

<?php
namespace IMooc;

class Factory
{
    static function createDatabase()
    {
        $db = Database::getInstance();
        Register::set("db1", $db);
        return $db;
    }
}

<?php
namespace IMooc;

class Register
{
    protected $objects;

    static function set($alias, $object)
    {
        self::$objects[$alias] = $object;
    }

    static function get($alias)
    {
        return self::$objects[$alias];
    }

    function _unset($alias)
    {
        unset(self::$objects[$alias]);
    }
}