$connection = new AMQPStreamConnection('localhost', 5672, '*', '*');
$channel = $connection->channel();
$channel->queue_declare('rpc_queue', false, false, false, false);

$callback = function($req) {

    $request = json_decode($req->body);

    $someclass = new SomeClass();
    $response = $someclass->someFunction($request);

    $msg = new AMQPMessage(json_encode($response), array('correlation_id' => $req->get('correlation_id')));
    $req->delivery_info['channel']->basic_publish($msg, '', $req->get('reply_to'));
    $req->delivery_info['channel']->basic_ack($req->delivery_info['delivery_tag']);

};

$channel->basic_qos(null, 1, null);
$channel->basic_consume('rpc_queue', '', false, false, false, false, $callback);

while(count($channel->callbacks)) {
    $channel->wait();
}

$channel->close();
$connection->close();

class RPCClient {

private IConnection connection;
private IModel channel;
private string replyQueueName;
private QueueingBasicConsumer consumer;

public RPCClient(){
    try{
        var factory = new ConnectionFactory() { HostName = Conf.hostName, UserName = Conf.userName, Password = Conf.password, RequestedHeartbeat = Conf.heartbeat, AutomaticRecoveryEnabled = true, TopologyRecoveryEnabled = true };
        connection = factory.CreateConnection();
        channel = connection.CreateModel();
        replyQueueName = channel.QueueDeclare().QueueName;
        consumer = new QueueingBasicConsumer(channel);
        channel.BasicConsume(queue: replyQueueName, noAck: true, consumer: consumer);
    } catch (Exception e){}
}

public string Call(string message) {

    var corrId = Guid.NewGuid().ToString();
    var props = channel.CreateBasicProperties();
    props.ReplyTo = replyQueueName;
    props.CorrelationId = corrId;

    var messageBytes = Encoding.UTF8.GetBytes(message);
    channel.BasicPublish(exchange: "", routingKey: "rpc_queue", basicProperties: props, body: messageBytes);

    while (true){
        var ea = (BasicDeliverEventArgs)consumer.Queue.Dequeue();

        if (ea.BasicProperties.CorrelationId == corrId){
            return Encoding.UTF8.GetString(ea.Body);
        }
    }
}

public void Close(){
    connection.Close();
}