问Datastax - Cassandra php-driver:未捕获Cassandra\Exception\LogicException：

EN

    PHP Fatal error:  Uncaught Cassandra\Exception\LogicException: Not    implemented in /home/philip/Documents/test.php:3
Stack trace:
#0 /home/user/Documents/test.php(3): Cassandra\Cluster\Builder->build()
#1 {main}
  thrown in /home/user/Documents/test.php on line 3

 <?php
// Connect to the cluster and keyspace "killrvideo"
$cluster  = Cassandra::cluster()->build();
$keyspace  = 'killrvideo';
$session  = $cluster->connect($keyspace);