Without a receipt header your application will fire messages potentially faster than the broker can receive them at. The broker may issue failure notices however STOMP being asynchronous your client won't get to see it.
Without a receipt ActiveMQ (5.5.0) with ProducerFlowControl turned on drops messages (even persistent ones) and my application knows nothing about it (send() returned true). With receipt header specified the STOMP library handles the wait for the receipt acknowledgement for you - you are essentially automatically throttled.
(PECL stomp >= 0.1.0)
Stomp::send -- stomp_send — Sends a message
Object oriented style (method):
Sends a message to the Message Broker.
Procedural style only: The stomp link identifier returned by stomp_connect().
Where to send the message
Message to send.
Associative array containing the additional headers (example: receipt).
TRUE on success or
FALSE on failure.
A transaction header may be specified, indicating that the message acknowledgment should be part of the named transaction.
Stomp is inherently asynchronous. Synchronous communication can be implemented adding a receipt header. This will cause methods to not return anything until the server has acknowledged receipt of the message or until read timeout was reached.