You can try something like

Queue::getIron()->getMessageById($queue_name, $msg_id)

which calls API if you use Iron.io queues.

Depending on the driver you are using you can see the contents of the queue. For example with the database driver it is a simple table and it has the details of the jobs "serialized". you could check those details.

But why do you want to check that? Avoid a job doing one thing twice? Maybe the job should do some validations when it runs and its not the queue that should be responsible of know what it has queued.

There are some packages out there like "queue monitor" or "queue checker"

Sorry, pasted the response in the wrong thread.

Luckily it at least had something to do :P