MySQL Locking Question

I'm preparing to write a DB app using PHP as the programming interface. I need to be able to lock records at certain points. I was wondering if the following is possible using PHP. 1. I want to use the GET_LOCK(str, timeout) function to lock records based on the record ID. Can GET_LOCK be called through PHP?? 2. If the GET_LOCK fails (Someone else allready has the lock for that record), I want to make the PHP code to continue attempting to GET_LOCK until it is available. Can you do events every 5 seconds until success in PHP? THANKS!