- Enh #4520: yii\caching/MemCache.php add sasl support (xjflyttp)

thanks.
because in https://code.google.com/p/memcached/wiki/SASLHowto
Running Memcached

In order to enable SASL support in the server you must use the -S flag.

The -S flag does a few things things:

    Enable all of the SASL commands.
    Require binary protocol only.
    Require authentication to have been successful before commands may be issued on a connection. 

I'm test by Aliyun VPS need this binary protocol options .