Right now we have issue with API reference S3 bucket, but you can take a look at phpdocs:
https://github.com/couchbase/php-couchbase/blob/master/stub/CouchbaseBucket.class.php#L135-L146
Also you can specify timeouts through cluster URL
http://developer.couchbase.com/documentation/server/current/sdk/php/client-settings.html
Or you setter method for that:
https://github.com/couchbase/php-couchbase/blob/master/stub/CouchbaseBucket.class.php#L543
For example:
$bucket->operationTimeout(500000); // 500k microseconds = 0.5 second