Description:
------------
AMQP_NOACK mean don't need to ack(). 
This method should used with a message this is retrieved without the AMQP_NOACK 
flag. 


<?php

/* Create a connection using all default credentials: */
$connection = new AMQPConnection();
$connection->connect();

/* create a queue object */
$queue = new AMQPQueue($connection);

//declare the queue
$queue->declare('myqueue');

//get the next message, but don't mark it as delivered
$message = $queue->get(0);

echo $message['msg'];

//acknowledge the message as received
$queue->ack($message['delivery_tag']);

?>
---
From manual page: http://www.php.net/amqpqueue.ack#refsect1-amqpqueue.ack-
description
---