Mysql is also very easy to learn, and really, there's not a lot that you actually have to learn to get it to do what you want. Experience mostly just helps in getting the info faster and more efficiently.
Of the two, I'd begin with PHP. It's a little easier to understand. However, it's a server-side language, so you'll require a host to run the programs. You can set up a local-host on your computer, but it's not super simple. (If you have a little cash, just buy a cheap shared-hosting site and work on there. That's what I did).
All that said, my recommendation is to learn Python. From all the research I did it's by far the easiest to learn and use. You can even use it for server-side programming instead of PHP. (Although I didn't try it, it looks far more complicated to get it running than PHP. -Python 3 that is-)
Even if you don't end up using Python, the lessons you learn from it will allow you to quickly pick up any programming language you choose to learn. Programming is a major challenge, Python makes it as easy as possible.