On PHPMaster.com today they've posted a new tutorial that helps you get started adding queuing to your application with PHP and RabbitMQ.

RabbitMQ is open-source message brokering software written in Erlang. The MQ in its name refers to a standard known as Advanced Message Queuing Protocol. For our purposes, and most others, it acts as a middleman between producer (sending) and consumer (receiving) programs - it simply accepts and forwards messages. [...] Both producers and consumers can be written in any language that has an available RabbitMQ or AMQP client library. In this article, I'll demo a producer program written in PHP and a consuming program in Python.

He walks you through the installation for both RabbitMQ itself and the PHP (php-amqlib) and Python (pika) tools to use for the interfaces. There's some details on how the queuing system works and the code for the sample clients is included as well as commands to use the two clients to send/receive messages.