PHP Cassandra构建集群

I am trying to get some example php code for connecting to a cassandra cluster. The problem I am having is that I do not get any output from retriving the data from the node. I limited the problem to this piece of code.

  $cluster   = Cassandra::cluster()                 
             ->build();

Here is the rest of the code for reference.

<?php
$cluster   = Cassandra::cluster()                 // connects to localhost by default
                 ->build();
$keyspace  = 'system';
$session   = $cluster->connect($keyspace);        // create session, optionally scoped to a keyspace
$statement = new Cassandra\SimpleStatement(       // also supports prepared and batch statements
    'SELECT keyspace_name, columnfamily_name FROM schema_columnfamilies'
);
$future    = $session->executeAsync($statement);  // fully asynchronous and easy parallel execution
$result    = $future->get();                      // wait for the result, with an optional timeout

foreach ($result as $row) {                       // results and rows implement Iterator, Countable and ArrayAccess
    printf("The keyspace %s has a table called %s
", $row['keyspace_name'], $row['columnfamily_name']);
}

?>