Não é possível conectar o Redis Cluster no Elaticache ao PHP usando a biblioteca phpredis

try{ 
    // Put your AWS ElastiCache Configuration Endpoint here.
    $servers  = ['aliceredis.8xyzwu.clustercfg.euw2.cache.amazonaws.com:6379'];
    // Tell client to use 'cluster' mode.
    $options  = ['cluster' => 'redis'];
    // Create your redis client
    $redis = new Predis\Client($servers, $options); 

    // Do something you want:
    // Set the expiration for 7 seconds
    $redis->set("tm", "I have data for 7s.");
    $redis->expire("tm", 7);
    $ttl = $redis->ttl("tm"); // will be 7 seconds

    // Print out value of the key 'tm'
    var_dump(array("msg"=>"Successfully connected to Redis Cluster.", "val"=>$redis->get("tm"))) ;

}
catch(Exception $ex){ 
    echo ('Error: ' . $ex->getMessage() ); // output error message.
}