Answer two PHP & MySQL questions on queues and transactions with PDO

I need someone to answer two PHP and MySQL questions I asked on StackOverflow but haven't gotten answers for yet (I need answers fast and can't wait). The questions are related to implementing a queue in PHP & MySQL and on how to use transactions with PDO. This will probably only take 10-15 minutes for someone experienced in these areas, plus if your answers turn out to be the best on SO then you'll get points on the site. Win-win. Do not apply for the job unless you are very experienced with PHP & MySQL, have knowledge and experience in implementing queues in them, and are experienced with PDO. Also, if your answer is unclear and I ask for clarification, you must be willing to edit/update your answer (or answer my request for clarification via chat on here).