elasticsearch\Connection $auth

Authentication data used to connect to the ElasticSearch node.

Array elements:

• username: the username for authentication.
• password: the password for authentication.

Array either MUST contain both username and password on not contain any authentication credentials.

See also http://www.elasticsearch.org/guide/en/elasticsearch/client/php-api/current/_configuration.html#_example_configuring_http_basic_auth.