On PHPMaster.com today there's a new article introducing you to the Command design pattern and looking to help you understand its use a bit better.

The majority of [cell phone] users have opted to receive an email, but a significant number are now opting to receive the notifications via SMS. Here’s the problem: How do you send a message via two different channels to both groups of users? The logical approach would be to split the users into 2 groups, email recipients and SMS recipients, which would involve running 2 different queries and sending the codeword to each group separately. Using the Command Pattern, which I will introduce you to in this article, you can send the message to both groups of users in a single process.

He uses the message queue he mentioned as an example - showing how you can can queue up different kinds of objects (actions) based on a common interface into the same process. He creates a "DailyAlertEmail" and "DailyAlertSMS" classes, both with a "send" method. The settings for these are then pulled from a database and the "execute" method on the "MessageQueue" class is called to loop through them, calling "send" to do that work.