Memcached connect problem

Hi there,

I've used CI 2.x to connect Memcached server. Now I want to convert the old source to CI 3.x but I got trouble with memcached conenct.

When I use basic PHP function to create Memcached object and connect, It's running normally.
And then I use CI 3.x memcached driver to connect it return FALSE.

I've tried this: $this->load->driver('cache', array('adapter' => 'memcached')); it return 500 HTTP code.

Somebody give me the suggestion?