class Cache
{
    public static function create($adapter, array $params)
    {
        $class_name = 'Cache_Adapter_' . $adapter;

        return new $class_name($params);
    }
}

abstract class Cache_Adapter
{
    public function __construct(array $params)
    {

    }
}

class Cache_Adapter_File extends Cache_Adapter
{
    // ...
}

// config.php
return array(
    'cache' => array(
        'adapter' => 'file',
        'params' => array(
            'path' => '/path',
        ),
    ),
);

// bootstrap.php
$dic->cache = Cache::create($config['cache']['adapter'], $config['cache']['params']);

// config.php
return array(
    'db1' => array(
        'adapter' => 'mysql',
        'params' => array(
            'user' => 'root',
            'connect_timeout' => 5,
        ),
    ),
    'db2' => array(
        'adapter' => 'sqlsrv',
        'params' => array(
            'db' => 'foo',
        ),
    ),
);

// bootstrap.php
$dic->db1 = Site:Db::create($config['db1']['adapter'], $config['db1']['params']);
$dic->db2 = Site:Db::create($config['db2']['adapter'], $config['db2']['params']);

class Cache_Adapter_Db extends Cache_Adapter
{
    // Instead of abstract Cache_Adapter::__construct(array $params)
    // something like this is needed:
    // public function __construct(array $params, Db_Adapter $db)
    public function __construct(array $params)
    {

    }
}

class Cache_Adapter_Db extends Cache_Adapter
{
    public function __construct(array $params, Db_Adapter $db)
    {
       parent::__construct($params);
    }
}

class Cache
{
    public static function create($adapter, array $params, $optparams = null )
    {
        $class_name = 'Cache_Adapter_' . $adapter;

        return new $class_name($params, $optparams);
    }
}

// config.php
return array(
    'db1' => array(
        'adapter' => 'mysql',
        'params' => array(
            'user' => 'root',
            'connect_timeout' => 5,
        ),
    ),
    'db2' => array(
        'adapter' => 'sqlsrv',
        'params' => array(
            'db' => 'foo',
        ),
        'options' => 'extraoption'
    ),
);

$dic->db2 = Site:Db::create(
   $config['db2']['adapter'],
   $config['db2']['params'],
   $config['db2']['options']
);